Selective inhibition of polyglutamine protein expression

ABSTRACT

The present invention relates to the selective inhibition of protein expression of CAG repeat-related disease proteins such as Huntington using nucleic acid analogs. Peptide nucleic acids and locked nucleic acids are particularly useful analogs.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/056,556, filed as a national phase application under 35 U.S.C. §371of International Application No. PCT/US2009/051938, filed Jul. 28, 2009,which claims benefit of priority to U.S. Provisional Application No.61/084,350, filed Jul. 29, 2008, the entire contents of each of whichare hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Grant No. 60642awarded by the National Institutes of Health-NIGMS. The Government hascertain rights in the invention.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The invention relates to the fields of biology and medicine. Moreparticularly, the invention provides compositions and methods for theselective inhibition of triplet-encoded disease protein expression, suchas Huntingtin and Ataxins 1-3.

B. Related Art

Huntington's Disease (HD) is an autosomal dominant inherited disorderwith a incidence of 5-10 per 100,000 individuals in Europe and NorthAmerica (Borrell-Pages et al., 2004; Walker, 2007). HD is caused by theexpansion of CAG trinucleotide repeats within the first exon of thehuntingtin (HTT) gene, leading to disruption of protein function, andneurodegeneration (Gusella and MacDonald, 2006). Antisenseoligonucleotides or siRNAs that reduce HTT expression have been proposedas a therapeutic strategy (Hasholt et al., 2003; Boado et al., 2002;Harper et al., 2005; Denovan-Wright and Davidson, 2006; DiFiglia et al.,2007) but most oligomers inhibit the mutant and wild-type proteinexpression indiscriminately. HTT is known to play an essential role inembryogenesis (Nasir et al., 1995), neurogenesis (White et al., 1997),and normal adult function in heterozygotes (Nasir et al., 1995),suggesting that agents inhibiting both mutant and wild-type HTT willinduce significant side-effects. One strategy for distinguishing mutantfrom wild-type alleles for HD and other neurological diseases usessiRNAs that target single nucleotide differences (Schwarz et al., 2006;Rodriguez-Lebron and Paulson, 2006). These polymorphisms will oftendiffer from patient to patient, complicating application ofallele-specific RNAi in the clinic. Thus, there remains a need toidentify agents that selectively inhibit mutant HTT production.

SUMMARY OF THE INVENTION

Thus, in accordance with the present invention, there is provided amethod for inhibiting expression of a disease protein encoded by an mRNAhaving expanded tri-nucleotide repeat region comprising contacting acell that produces said disease protein with an amount of a nucleic acidanalog that targets said repeat region in said mRNA, wherein (i)inhibiting is selective for said disease protein over a normal form ofsaid disease protein, an mRNA for which lacks an expanded tri-nucleotiderepeat region, and (ii) inhibiting does not substantially affectproduction of said mRNA. The repeat region may be about 151 repeats or125 repeats or less in size. The disease protein may be Huntingtin,ataxin-3, ataxin-1, ataxin-2 or atrophin1

The nucleic acid analog may be about 7 to about 30 bases in length. Thenucleic acid analog may be a peptide-nucleic acid (PNA) or a lockednucleic acid (LNA), may further comprise a cationic peptide, and/or mayfurther target the junction of a tri-nucleotide repeat region. Thenucleic acid analog may lack bases that recruit RNAseH. The nucleic acidanalog may be formulated in a lipid vehicle. The PNA may comprise atleast one modifed base, such as[bis-o-(aminoethoxy)phenyl]pyrrolocytosine.

In another embodiment, there is provided a method for inhibitingexpression, in a subject, of a disease protein encoded by an mRNA havingexpanded tri-nucleotide repeat region comprising administering to saidsubject an amount of a nucleic acid analog that targets said repeatregion in said mRNA, wherein (i) inhibiting is selective for saiddisease protein over a normal form of said disease protein, an mRNA forwhich lacks an expanded tri-nucleotide repeat region, and (ii)inhibiting does not substantially affect production of said mRNA. Therepeat region may be about 151 repeats or 125 repeats or less in size.The disease protein may be Huntingtin, ataxin-3, ataxin-1, ataxin-2 oratrophin1.

The nucleic acid analog may be about 7 to about 30 bases in length. Thenucleic acid analog may be a peptide-nucleic acid (PNA) or a lockednucleic acid (LNA), may further comprise a cationic peptide, and/or mayfurther target the junction of a tri-nucleotide repeat region. The PNAmay comprise at least one modifed base, such as[bis-o-(aminoethoxy)phenyl]pyrrolocytosine. The nucleic acid analog maylack bases that recruit RNAseH. The nucleic acid analog may administeredmore than one, such as at least about once every week. The nucleic acidanalog may be administered orally, intravenously, intraarterially,intramuscularly or into the CNS. The nucleic acid analog may beadministered in a lipid formulation. The method may further comprisingadministering a second therapy to said subject.

In yet another embodiment, there is provided a composition of mattercomprising a nucleic acid analog that targets an mRNA encoding anexpanded tri-nucleotide repeat region for a disease protein. The nucleicacid analog may target said repeat region, and may further target arepeat region junction. The nucleic acid analog may be about 7 to about30 bases in length. The nucleic acid analog may be a peptide-nucleicacid (PNA) or a locked nucleic acid (LNA), and may further comprise acationic peptide. The PNA may comprise at least one modifed base, suchas [bis-o-(aminoethoxy)phenyl]pyrrolocytosine. The nucleic acid analogmay lack bases that recruit RNAseH. The nucleic acid analog may bedispersed in a lipid vehicle.

It is contemplated that any method or composition described herein canbe implemented with respect to any other method or composition describedherein.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.”

These, and other, embodiments of the invention will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingvarious embodiments of the invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manysubstitutions, modifications, additions and/or rearrangements may bemade within the scope of the invention without departing from the spiritthereof, and the invention includes all such substitutions,modifications, additions and/or rearrangements.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawing form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better undsrstood by reference to thesedrawing and the detailed description presented below.

FIGS. 1A-D. Triplet repeats as targets for synthetic oligomers. (FIG.1A) Schematic of the CONTRAfo1d prediction of the HTT CAG triplet repeatand adjacent RNA regions. Predicted hairpin structure is larger for theexpanded mutant repeats than for the wild-type repeat region (CAG repeatregion shown in red). Because of space constraints, the length of thehairpin containing the mutant CAG sequence is not drawn to scale. Thedifferences between mutant and wild-type repeats in GM04281cells wouldbe larger. (FIG. 1B) Western analysis showing that wild-type and mutantHTT protein can be separated by gel electrophoresis. The left lane showsHTT from GM04795, a fibroblast cell line that is homozygous forwild-type HTT. The right lane shows HTT from GM04281, a fibroblast cellline that is heterozygous for mutant HTT. (FIG. 1C) Chemical structuresof PNA and LNA. (FIG. 1D) Target sites for oligomers within HTT mRNA (NM—002111). The HTT gene is shown from +121to 300SEQ ID NO:29). The AUGtranslation start is italicized, the CAG repeat region is in bold-face(to save space the inventors show only 21repeats, more repeats would bepresent in repeat regions from HD patients).

FIGS. 2A-F. Inhibition to HTT expression by PNA-peptide conjugates. Alldata show western analysis of protein levels. Unless otherwise notedexperiments use GM04281 fibroblast cells that are heterozygous formutant HTT expression. (FIG. 2A) Effect on HTT expression of adding 5μMPNA-peptide conjugates to GM04281cells. (FIG. 2B) Effect on HTTexpression of adding increasing concentrations of PNA conjugate REP.(FIG. 2C) Effect on HTT expression of adding increasing concentrationsof PNA conjugate 3J-8. (FIG. 2D) Timecourse of inhibition of HTTexpression by PNA conjugate REP (1 μM) for 2-14 days after transfection.(FIG. 2E) Effect of adding REP on expression of other proteins withmRNAs that contain CAG repeats. (FIG. 2F) Glutamate-induced apoptosis ofWT and YAC128 mouse striatal neurons (MSN) treated with or without PNAconjugates. PNA conjugate REP were added at the concentration of 0.25 μMand 0.5 μM, 4 days before the glutamate application. NoncomplementaryPNA conjugate −CTL1 was added at 0.5 μM. MSN were exposed to 250 μMglutamate for 7 h, fixed, permeabilized and analyzed by TUNEL stainingand PI counterstaining. The fraction of TUNEL-positive is shown for WT(open bars) and YAC128 (filled bars) MSN. The data are presented asmean±SE (n=6-8 microscopic fields, 100-300 MSN per field). Apoptosis ofYAC128 MSN is significantly (p<0.05) reduced by the addition of REP whentreated with 250 μM glutamate. Data representative of duplicateexperiments.

FIGS. 3A-F. Inhibition of HTT expression by modified PNA designs andLNAs. All data show western analysis of protein levels in GM04281fibroblast cells. Effect on HTT expression of adding increasingconcentrations of REP16 (FIG. 3A) or REP13 (FIG. 3B). (FIG. 3C) Effecton HTT expression of adding increasing concentrations of REP-N-K₈. (FIG.3D) Effect on HTT expression of 2 μM PNA conjugates 3J-0, 3J-4, 3J-6,3J-8, and 3J-10 that target related sequences at the 3′ junction. (FIG.3E) Effect on HTT expression of adding 100 nM concentrations of LNAs.(FIG. 3F) Effect of adding LNA/REP on expression of other proteins withmRNAs that contain CAG repeats.

FIGS. 4A-E. Potent and selective inhibition of mutant ataxin-3. All datashow western analysis of ataxin-3expression in GM06151fibroblast cells.(FIG. 4A) Target sites for oligomers within the ataxin-3gene (SEQ IDNO:30). (FIG. 4B) Inhibition of ataxin-3expression by PNA conjugateREP19. (FIG. 4C) Inhibition of ataxin-3expression by PNA conjugateREP13. (FIG. 4D) Inhibition of ataxin-3expression by PNA conjugate5J/ATX. (FIG. 4E) Inhibition of ataxin-3expression by PNA conjugate3JATX.

FIGS. 5A-B. Anti-HTT PNAs do not reduce HTT mRNA levels. (FIG. 5A)Effect on adding PNA-peptide conjugates on expression of HTT protein(western analysis, left) and HTT mRNA (quantitative PCR, right) inGM04281 fibroblast cells. All conjugates were added at a concentrationof 1 μM (FIG. 5B) Effect of adding PNA-peptide conjugate REP or −CTL1 at0.5, 1 and 2 μM on levels of HTT protein (western analysis, left) ormRNA (quantitative PCR, right). NT=no treatment (no conjugate added).

FIG. 6. Inhibition of neuronal/cell glial cell mixture by PNA REP. HTTprotein levels were analyzed by western analysis. PNAs REP or −CTL1 wereadded at the indicated concentrations. Medium striatal spiny neurons(MSN) and supporting glial cells were harvested from mice and culturedas described in Materials and Methods. Levels of inhibition reflect HTTlevels in both glial and MSN cells. Because glial cells make up a largemajority (˜90%) of the cells in culture, data should not be taken as adirect indication of the level of inhibition of HTT in MSN cells. Cellswere treated with PNA and harvested in parallel with cells used formneuroprotection assays (FIG. 2F). The top HTT band is human HTT, thebottom is murine HTT.

FIGS. 7A-D. Inhibition of HTT expression by duplex RNAs. All data showwestern analysis of protein levels in GM04281 fibroblast cells. (FIG.7A) Effect on HTT expression of adding 100 nM concentrations of duplexsiRNAs. (FIG. 7B) Effect on HTT expression of adding increasingconcentrations of siRNA/REP. (FIG. 7C) Effect on HTT expression ofadding increasing concentrations of siRNA/5J. (FIG. 7D) Effect on HTTexpression of adding increasing concentrations of siRNA/3J. Duplex RNAswere introduced using cationic lipid.

FIGS. 8A-D. Western analysis. Effect of adding increasing concentrationsof LNA/3J (FIG. 8A), LNA/5J (FIG. 8B), LNA/+CTL (FIG. 8C) or LNA/REP(FIG. 8D) on HTT protein expression in GM04281 fibroblast cells. LNAswere introduced using cationic lipid.

FIG. 9. Inhibition of ataxin-3 expression by siRNA/REP. Data showwestern analysis of protein levels in GM06151 fibroblast cells. Effecton ataxin expression of adding increasing concentrations of siRNA/REP.Duplex RNAs were introduced using cationic lipid.

FIG. 10. Structure of [bis-o-(aminoethoxy)phenyl]pyrrolocytosine.

FIGS. 11A-F. Modified PNAs selectively inhibit mutant HTT expression infibroblasts GM04281. (FIG. 11A) Top, western analysis the effects ofPNAs I-VI on HTT expression. Bottom, quantitation of inhibition ofmutant and wild-type HTT by PNAs I-VI. PNAs were added at 1 μMconcentration. (FIGS. 11B-F) Effects of PNAs II-VI on HTT expression atvaried concentrations. Experiments were performed in triplicate.Expression is relative to expression to untreated cells.

FIGS. 12A-C. Fluorescent microscopy of PNA 11 in living fibroblasts. PNAwas added at 1 μM concentration. (FIG. 12A) One day or (FIG. 12B) ninedays after PNA transfection. Left, Differential interference contrastmicroscopy (DIC) image; middle, PNA fluorescent; right, overlay of DICand fluorescent images. (FIG. 12C) PNA was co-localized with endosomemarker Transferrin. 1 μM of Htt2 was co-incubate with 25 μg/mL ofTransferrin-Alexa Fluor 633 for 15 h in fibroblast cells. Upper left,DIC image; upper right, PNA alone; lower left, transferrin fluorescent;lower right, overlay of PNA and transferrin images.

DETAILED DESCRIPTION OF THE INVENTION

As discussed above, CAG-repeat related diseases present significantobstacles with respect to the selective inhibition of disease versusnormal protein production. As shown in the data here presented by theinventors, single-stranded nucleic acid analogs (NAAs) can exploitdifferences in the number of triplet repeats and can achieveallele-selective inhibition of expression of HTT or ataxin-3.Selectivity is achieved even though complementary target sequences alsoexist within both mutant and wild-type mRNAs. For HTT, the target can bewithin the CAG repeat or at the 3′ junction between the repeat and therest of the HTT gene. For ataxin-3, the repeat, the 3′ junction, and the5′ junction arc all productive targets Inhibition is robust and can beachieved by a wide range of different PNAs and LNAs. The broad base ofinhibitory compounds permits design of improved agents with enhancedpotencies and selectivities.

Two observations are worth making. The first is that single-strandedNAAs can discriminate among identical sequences inside cells on thebasis of context—in this case length of the repeat and the potential toform energetically different structures—rather than sequence. The secondis that the potential for developing single-stranded analogs astreatment for genetic disease appears greater than had been appreciated.Exploiting the surprising ability of NAAs to selectively recognizemutant repeat nucleic acid sequences offers a promising strategy fordeveloping therapies for Huntington's Disease, Machado-Joseph Disease,spinocerebellar ataxias and other triplet repeat disorders.

I. Polyglutamine Repeat Diseases

The polyglutamine disorders include nine neurodegenerative disordersthat are inherited gain-of-function diseases caused by expansion of atranslated CAG repeat. Even though the disease-causing proteins arewidely expressed, specific collections of neurons are more susceptiblein each disease. There is substantial evidence linking the function ofthe polyglutamine disease-associated proteins with the regulation ofgene transcription, and a variety of mechanisms have been suggested bywhich the polyglutamine proteins impact upon transcription, includingaltering the function of a very specific DNA-binding factor like the AR(SBMA), general DNA-binding proteins like TBP (SCA17), Sp1, TFIID andTFIIF (HD), chromatin structure (SCAT), coregulators (HD, SCA1, andDRPLA), and possibly the ubiquitin-proteasome system (SCA3). There alsois evidence they impact other biological processes important forneuronal function, for example, intracellular trafficking (Gunawardenaand Goldstein, 2005) and the mitochondrial/energy metabolism (Browne andBeal, 2004). Some of these disorders are discussed in greater detailbelow.

A. Huntington Disease

Huntington disease, also called Huntington's chorea, chorea major, orHD, is a genetic neurological disorder characterized by abnormal bodymovements called chorea and a lack of coordination; it also affects anumber of mental abilities and some aspects of behavior. In 1993, thegene causing HD was found, making it one of the first inherited geneticdisorders for which an accurate test could be performed. The accessionnumber for Huntingtin is NM_002111.

The gene causing the disorder is dominant and may, therefore, beinherited from a single parent. Global incidence varies, from 3 to 7 per100,000 people of Western European descent, down to 1 per 1,000,000 ofAsian and African descent. The onset of physical symptoms in HD occur ina large range around a mean of a person's late forties to early fifties.If symptoms become noticeable before a person is the age of twenty, thentheir condition is known as Juvenile HD.

A trinucleotide repeat expansion occurs in the Huntingtin gene, whichproduces mutant Huntingtin protein. The presence of this proteinincreases the rate of neuron cell death in select areas of the brain,affecting certain neurological functions. The loss of neurons isn'tfatal, but complications caused by symptoms reduce life expectancy.There is currently no proven cure, so symptoms are managed with a rangeof medications and supportive services.

Symptoms increase in severity progressively, but are not oftenrecognised until they reach certain stages. Physical symptoms areusually the first to cause problems and be noticed, but these areaccompanied by cognitive and psychiatric ones which aren't oftenrecognized. Almost everyone with HD eventually exhibits all physicalsymptoms, but cognitive symptoms vary, and so any psychopathologicalproblems caused by these, also vary per individual. The symptoms ofjuvenile HD differ in that they generally progress faster and are morelikely to exhibit rigidity and bradykinesia instead of chorea and ofteninclude seizures.

The most characteristic symptoms are jerky, random, and uncontrollablemovements called chorea, although sometimes very slow movement andstiffness (bradykinesia, dystonia) can occur instead or in later stages.These abnormal movements are initially exhibited as general lack ofcoordination, an unsteady gait and slurring of speech. As the diseaseprogresses, any function that requires muscle control is affected, thiscauses reduced physical stability, abnormal facial expression, impairedspeech comprehensibility, and difficulties chewing and swallowing.Eating difficulties commonly cause weight loss. HD has been associatedwith sleep cycle disturbances, including insomnia and rapid eye movementsleep alterations.

Selective cognitive abilities are progressively impaired, includingexecutive function (planning, cognitive flexibility, abstract thinking,rule acquisition, initiating appropriate actions and inhibitinginappropriate actions), psychomotor function (slowing of thoughtprocesses to control muscles), perceptual and spatial skills of self andsurrounding environment, selection of correct methods of rememberinginformation (but not actual memory itself), short-term memory, andability to learn new skills, depending on the pathology of theindividual.

Psychopathological symptoms vary more than cognitive and physical ones,and may include anxiety, depression, a reduced display of emotions(blunted affect) and decreased ability to recognize negative expressionslike anger, disgust, fear or sadness in others, egocentrism, aggression,and compulsive behavior. The latter can cause, or worsen, hypersexualityand addictions such as alcoholism and gambling.

HD is autosomal dominant, needing only one affected allele from eitherparent to inherit the disease. Although this generally means there is aone in two chance of inheriting the disorder from an affected parent,the inheritance of HD is more complex due to potential dynamicmutations, where DNA replication does not produce an exact copy ofitself. This can cause the number of repeats to change in successivegenerations. This can mean that a parent with a count close to thethreshold, may pass on a gene with a count either side of the threshold.Repeat counts maternally inherited are usually similar, whereaspaternally inherited ones tend to increase. This potential increase inrepeats in successive generations is known as anticipation. In familieswhere neither parent has HD, new mutations account for truly sporadiccases of the disease. The frequency of these de novo mutations isextremely low.

Homozygous individuals, who carry two mutated genes because both parentspassed on one, are rare. While HD seemed to be the first disease forwhich homozygotes did not differ in clinical expression or course fromtypical heterozygotes, more recent analysis suggest that homozygosityaffects the phenotype and the rate of disease progression though it doesnot alter the age of onset suggesting that the mechanisms underlying theonset and the progression are different.

Huntingtin protein is variable in its structure as there are manypolymorphisms of the gene which can lead to variable numbers ofglutamine residues present in the protein. In its wild-type (normal)form, it contains 6-35 glutamine residues; however, in individualsaffected by HD, it contains between 36-155 glutamine residues.Huntingtin has a predicted mass of ˜350 kDa, however, this varies and islargely dependent on the number of glutamine residues in the protein.Normal huntingtin is generally accepted to be 3144 amino acids in size.

Two transcriptional pathways are more extensively implicated in HD—theCBP/p300 and Sp1 pathways—and these are transcription factors whosefunctions are vital for the expression of many genes. The postulatedrelationship between CBP and HD stems from studies showing that CBP isfound in polyglutamine aggregates (see Kazantsev et al., 1999).Consequently, it was demonstrated that huntingtin and CBP interact viatheir polyglutamine stretches, that huntingtin with an expandedpolyglutamine tract interferes with CBP-activated gene expression, andthat overexpression of CBP rescued polyglutamine-induced toxicity incultured cells (Nucifora et al., 2001; Steffan et al., 2001). Mutanthuntingtin was also shown to interact with the acetyltransferase domainof CBP and inhibit the acetyltransferase activity of CBP, p300, and thep300/CBP-associated factor P/CAF (Steffan et al., 2001).

These observations prompted a hypothesis whereby the pathogenic processwas linked to the state of histone acetylation; specifically, mutanthuntingtin induced a state of decreased histone acetylation and thusaltered gene expression. Support for this hypothesis was obtained in aDrosophila HD model expressing an N-terminal fragment of huntingtin withan expanded polyglutamine tract in the eye. Administration of inhibitorsof histone deacetylase arrested the neurodegeneration and lethality(Steffan et al., 2001). Protective effects of HDAC inhibitors have beenreported for other polyglutamine disorders, prompting the concept thatat least some of the observed effects in polyglutamine disorders are dueto alterations in histone acetylation (Hughes 2002). Studies publishedin 2002 revealed that the N-terminal fragment of huntingtin and intacthuntingtin interact with Sp1 (Dunah et al., 2002; Li et al., 2002), atranscriptional activator that binds to upstream GC-rich elements incertain promoters. It is the glutamine-rich transactivation domain ofSp1 that selectively binds and directs core components of the generaltranscriptional complex such as TFIID, TBP and other TBP-associatedfactors to Sp1-dependent sites of transcription. In vitro transcriptionstudies have gone on to show that in addition to targeting Sp1, mutanthuntingtin targets TFIID and TFIIF, members of the core transcriptionalcomplex (Zhai et al. 2005). Mutant huntingtin was shown to interact withthe RAP30 subunit of TFIIF. Notably, overexpression of RAP30 alleviatedboth mutant huntingtin-induced toxicity and transcriptional repressionof the dopamine D2 receptor gene. These results indicate that mutanthuntingtin may interfere with multiple components of the transcriptionmachinery.

There is no treatment to fully arrest the progression of the disease,but symptoms can be reduced or alleviated through the use of medicationand care methods. Huntington mice models exposed to better husbandrytechniques, especially better access to food and water, lived muchlonger than mice that were not well cared for.

Standard treatments to alleviate emotional symptoms include the use ofantidepressants and sedatives, with antipsychotics (in low doses) forpsychotic symptoms. Speech therapy helps by improving speech andswallowing methods; this therapy is more effective if started early on,as the ability to learn is reduced as the disease progresses. A two-yearpilot study, of intensive speech, pyschiatric and physical therapy,applied to inpatient rehabilitation, showed motor decline was greatlyreduced.

Nutrition is an important part of treatment; most third and fourth stageHD sufferers need two to three times the calories of the average personto maintain body weight. Healthier foods in pre-symptomatic and earlierstages may slow down the onset and progression of the disease. Highcalorie intake in pre-symptomatic and earlier stages has been shown tospeed up the onset and reduce IQ level. Thickening agent can be added todrinks as swallowing becomes more difficult, as thicker fluids areeasier and safer to swallow. The option of using a stomach PEG isavailable when eating becomes too hazardous or uncomfortable; thisgreatly reduces the chances of aspiration of food, and the subsequentincreased risk of pneumonia, and increases the amount of nutrients andcalories that can be ingested.

EPA, an Omega-3 fatty acid, may slow and possibly reverse theprogression of the disease. As of April 2008, it is in FDA clinicaltrial as ethyl-EPA, (brand name Miraxion), for prescription use.Clinical trials utilise 2 grams per day of EPA. In the United States, itis available over the counter in lower concentrations in Omega-3 andfish oil supplements.

B. Spinocerebellar Ataxias

Spinocerebellar ataxia (SCA) is one of a group of genetic disorderscharacterized by slowly progressive incoordination of gait and oftenassociated with poor coordination of hands, speech, and eye movements.Frequently, atrophy of the cerebellum occurs. As with other forms ofataxia, SCA results in unsteady and clumsy motion of the body due to afailure of the fine coordination of muscle movements, along with othersymptoms. The symptoms of the condition vary with the specific type(there are several), and with the individual patient. Generally, aperson with ataxia retains full mental capacity but may progressivelylose physical control.

There is no known cure for spinocerebellar ataxia, which is aprogressive disease (it gets worse with time), although not all typescause equally severe disability. Treatments are generally limited tosoftening symptoms, not the disease itself. The condition can beirreversible. A person with this disease will usually end up needing touse a wheelchair, and eventually they may need assistance to performdaily tasks. The treatment of incoordination or ataxia, then mostlyinvolves the use of adaptive devices to allow the ataxia individual tomaintain as much independence as possible. Such devices may include acane, crutches, walker, or wheelchair for those with impaired gait;devices to assist with writing, feeding, and self care if hand and armcoordination are impaired; and communication devices for those withimpaired speech.

Many patients with hereditary or idiopathic forms of ataxia have othersymptoms in addition to ataxia. Medications or other therapies might beappropriate for some of these symptoms, which could include tremor,stiffness, depression, spasticity, and sleep disorders, among others.Both onset of initial symptoms and duration of disease can be subject tovariation, and it can be easily misdiagnosed as another neurologicalcondition, such as multiple sclerosis (MS).

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant ataxiathat results in gait ataxia, dysarthria, and bulbar dysfunction, withdeath usually between 10 and 15 years after the onset of symptoms. Theaverage age of onset is in the 4^(th) decade of life. Despite theprotein ataxin-1 being widely expressed in the central nervous system,the most frequently seen and most severe pathological alterations arerestricted to loss of Purkinje cells in the cerebellar cortex, as wellas loss of neurons in the inferior olivary nuclei, the cerebellardentate nuclei and the red nuclei.

Normally ataxin-1, the product of the SCA1 gene, is prominently locatedin the nuclei of neurons (Servadio et al., 1995). Indication that SCA1pathogenesis was due to alterations in nuclear function began with theobservation that for mutant ataxin-1 to cause disease, it had to enterthe nucleus of Purkinje cells (Klement et al., 1998). Consequent studiesrevealed that wild-type ataxin-1 has properties consistent with a rolein the regulation of gene expression in the nucleus. These include theability to bind RNA (Yue et al., 2001) and to shuttle between thenucleus and cytoplasm (Irwin et al., 2005).

Spinocerebellar ataxia type 2 (SCA2) is characterized by progressivecerebellar ataxia, including nystagmus, slow saccadic eye movements and,in some individuals, ophthalmoparesis. Pyramidal findings are present;deep tendon reflexes are brisk early on and are absent later in thecourse. Age of onset is typically in the 3^(rd) to 4^(th) decade with a10-15-year disease duration.

The diagnosis of SCA2 rests upon the use of molecular genetic testing todetect an abnormal CAG trinucleotide repeat expansion of the ATXN2 gene.Affected individuals have alleles with greater than 32 CAG trinucleotiderepeats. Such testing detects nearly 100% of cases and is available inclinical laboratories.

Management of individuals with SCA2 is supportive. Affected individualsshould maintain activity. Canes and walkers help prevent falls; grabbars, raised toilet seats, and ramps to accommodate motorized chairs maybe necessary. Speech therapy and communication devices such as writingpads and computer-based devices may benefit those with dysarthria.Weighted eating utensils and dressing hooks help maintain a sense ofindependence. When dysphagia becomes troublesome, video esophagrams canidentify the consistency of food least likely to trigger aspiration.Vitamin supplements are recommended; weight control preventsdifficulties with ambulation and mobility. Affected individuals shouldavoid alcohol and medications known to affect cerebellar function.

Spinocerebellar ataxia type 3 (SCA3), also known as Machado Josephdisease (MJD), is the most common of the autosomal dominantly inheritedataxias with several genetic features that distinguish it from many ofthe other polyglutamine disorders. In contrast to HD and SCAT, where therepeat threshold for mutant alleles is <40, in SCA3 the repeat thresholdfor the mutant alleles is >50 repeats. Moreover, although otherpolyglutamine disorders behave as pure dominant diseases, SCA3/MJDhomozygous patients have a more severe disease presentation thanindividuals having only a single mutant allele. Onset is normally in the4^(th) decade, and duration averages about 10 years.

Ataxin-3 contains an N-terminal Josephin domain (JD) with recentlyascribed ubiquitin protease activity (Burnett et al., 2003; Scheel etal., 2003), two ubiquitin interacting motifs (UIMs) capable of bindingubiquitin (Chai et al., 2004; Burnett et al., 2003; Donaldson et al.,2003) followed by a polyglutamine stretch, and a C-terminal variabledomain. The crystal structure of the ataxin-3 JD provided insight intothe potential function of ataxin-3 as a polyubiquitin chain editingprotein by demonstrating a tight connection between polyubiquitinbinding and the deubiquitylating activity of ataxin-3 (Mao et al., 2005;Nicastro et al., 2005). Thus, there are considerable structural dataindicating that ataxin-3 has a role in the ubiquitin and/or theubiquitin-proteasome system. Ataxin-3 is unique from the otherpolyglutamine diseases in that wild-type ataxin-3 expression inDrosophila protects neurons from toxicity initiated by otherpolyglutamine-expanded proteins (Warrick et al., 2005). This protectionafforded by wild-type ataxin-3 was dependent on active protcasomes andboth the UIM and ubiquitin protease domains of ataxin-3.

The accession numbers for these genes arc as follows: Ataxin1(NM_000332), ataxin2 (NM_002973), and ataxin3 (NM_004993).

C. Dentatorubral and Pallidoluysian Atrophy (DRPLA)

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominantspinocerebellar degeneration caused by an expansion of a CAG repeatencoding a polyglutamine tract in the atrophin-1 protein. It is alsoknown as Haw River Syndrome and Naito-Oyanagi disease. Several sporadiccases have been reported from Western countries, but this disorder seemsto be very rare except in Japan.

DRPLA can be juvenile-onset (<20 years), early adult-onset (20-40years), or late adult-onset (>40 years). Late adult-onset DRPLA ischaracterized by ataxia, choreoathetosis and dementia. Early adult-onsetDRPLA also includes seizures and myoclonus. Juvenile-onset DRPLApresents with ataxia and symptoms consistent with progressive myoclonusepilepsy.

Atrophin-1 (ATN1) encodes a hydrophilic 1184 amino acid protein withseveral repetitive motifs including a serine-rich region, a variablelength polyglutamine tract, a polyproline tract, and a region ofalternating acidic and basic residues. It contains a putative nuclearlocalization signal in the N-terminus of the protein and a putativenuclear export signal in the C-terminus. ATN1 is ubiquitously expressedin all tissues, but proteolytically cleaved in neuronal cells. Thefunction of ATN1 is not clear, however it is believed to be atranscriptional co-repressor. ATN1 and atrophin-2 can beco-immunoprecipitated, indicating that they may carry out some functionstogether in a molecular complex. Atrophin-1 may be a dispensable orredundant protein as mice bred with a null allele for atrophin-1 produceviable and fertile offspring and show no compensatory upregulation ofatrophin-2 The accession number for atrophin1 is NM_001940.

DRPLA is characterized by marked, generalized brain atrophy and theaccumulation of atrophin-1 with expanded glutamine stretches. Mutantatrophin-1 proteins have been found in neuronal intranuclear inclusions(NII) and diffusely accumulated in the neuronal nuclei. While the roleof NIIs (pathologic or protective) is unclear, the diffuse accumulationof mutant protein is regarded as toxic. There is significant reductionin CNS tissue throughout the brain and spinal cord, with brain weightsof DRPLA patients often becoming less than 1000 g. In regions lackingobvious neuronal depletion, atrophy of the neuropil is noted. The globuspallidus (lateral greater than medial segment) and subthalamic nucleusdemonstrate consistent neuronal loss and astrocytic gliosis. The dentatenucleus shows neuronal loss with the remaining atrophic neuronsexhibiting grumose degeneration. In general, the pallidoluysiandegeneration is more severe than the dentatorubral degeneration injuvenile-onset and the reverse is true for the late adult-onset.

Transgenic DRPLA mice demonstrated several neuronal abnormalitiesincluding a reduction in the number and size of dendritic spines as wellas in the area of perikarya and diameter of dendrites. Spine morphologyand density have been linked to learning and memory functions as well asepilepsy. The stubby-type spines seen in DRPLA mice are morphologicallydifferent from the thin and mushroom-type spines seen in Huntington'smice.

Morphometric analysis of DRPLA mouse brains has shown a loss of normalinter-microtubule spacing in neuronal axons. The microtubules wererelatively compacted, suggesting abnormalities in protein transport mayplay a role in neuronal degeneration. In humans, atrophin-1 interactswith IRSp53, which interacts with Rho GTPases to regulate theorganization of the actin cytoskeleton and the pathways that regulatelamellipodia and filopodia.

Ms are not exclusive to DRPLA; they have been found in a variety ofneurodegenerative disorders. In DRPLA, Ms have been demonstrated in bothneurons and glial cells in the striatum, pontine nuclei, inferior olive,cerebellar cortex and dentate nucleus, though the incidence of neuronswith NIIs is low, roughly 1-3%. In DRPLA, the NIIs are spherical,eosinophilic structures of various sizes. They are non-membrane-boundand are composed of both granular and filamentous structures. They areubiquitinated and may be paired or in doublet form within the nucleus.

Ms have also been demonstrated to alter the distribution of theintranuclear structures, such as promyelocytic leukemia protein (PML)nuclear bodies. Although the role of PML bodies is unclear, they arebelieved to be involved in apoptosis. In neurons with NII, PML bodies inDRPLA patients form a shell or ring around the ubiquitinated core. Insimilar polyQ diseases, the association of this PML shell has been shownto be size-dependent with larger NIIs being PML negative. This has ledto two models, one in which PML bodies represent sites for NII formationand a second in which PML bodies are involved in degradation andprotcolysis of NIIs.

Filemcntous, atrophin-1 positive, inclusions are also observedexclusively in the cytoplasm of the dentate nucleus, which are extremelysimilar to the inclusions observed in the motor neurons in amyotrophiclateral sclerosis.

In DRPLA, diffuse accumulation of mutant ATN1 occurs far moreextensively than NII formation. The extent and frequency of neuronsshowing the diffuse nuclear accumulations changes depending on CAGrepeat length. It is believed that the diffuse nuclear accumulationscontribute to the clinical features such as dementia and epilepsy. ATN1contains both a nuclear localization sequence and a nuclear exportsequence. Cleavage of ATN1 to an N terminal fragment relieves ATN1 ofits nuclear export signal and concentrates it in the nucleus. Increasednuclear concentrations have been demonstrated via transfection assay toenhance cellular toxicity.

In both the juvenile and adult forms, regions in which more than 40% ofneurons became immunoreactive to 1C2 (a monoclonal antibody againstexpanded polyglutamine stretches) included: the nucleus basalis ofMeynert, large striatal neurons, globus pallidus, subthalamic nucleus,thalamic intralaminar nucleus, lateral geniculate body, oculomotornucleus, red nucleus, substantia nigra, trigeminal motor nucleus,nucleus raphe pontis, pontine nuclei, vestibular nucleus, inferior oliveand the cerebellar dentate nucleus. The juvenile type also showsreactivity in the cerebral cortex, hippocampal CA1 area, and thereticular formation of the brainstem. Nuclei containing accumulations ofmutant atrophin-1 are deformed with nuclear membrane indentations.

Diagnosis of DRPLA rests of positive family history, clinical findings,and genetic testing. Family history can be difficult to obtain if arelative was misdiagnosed, died young, or experiences late onset ofsymptoms. Other diseases in the differential diagnosis of adult-onsetDRPLA include Huntington's and the spinocerebellar ataxias. Forjuvenile-onset, familial essential myoclonus and epilepsy (FEME),Lafora, Unverricht-Lundborg, Neuroaxonal dystrophy, Gaucher's disease,Sialidosis, and Galactosialidosis. To quantify the extent of thedisease, an MRI, EEG and neuropsychological testing are recommended.Seizures are treated with anticonvulsants and psychiatric disturbanceswith psychotropic medications.

II. Nucleic Acid Analogs

A. Analogs

The present invention contemplates the use of nucleic acid analogs NAAsthat mimic single-stranded oligonucleotides in their ability tohybridize to target sequences, and in particular, to mRNAs containingexpanded CAG repeats. The NAAs include molecules coupled to peptides fortargeting and or stability. Two particular examples of NAAs are peptidenucleic acids and locked nucleic acids.

Peptide nucleic acids (PNAs) are nonionic DNA mimics that haveoutstanding potential for recognizing duplex DNA (Kaihatsu et al., 2004;Nielsen et al., 1991). PNAs can be readily synthesized and bind tocomplementary sequences by standard Watson-Crick base-pairing (Egholm etal., 1993), allowing them to target any sequence within the genomewithout the need for complex synthetic protocols or designconsiderations. Strand invasion of duplex DNA by PNAs is not hindered byphosphate-phosphate repulsion and is both rapid and stable (Kaihatsu etal., 2004; Nielsen et al., 1991). Applications for strand invasion byPNAs include creation of artificial primosomes (Demidov et al., 2001),inhibition of transcription (Larsen and Nielsen, 1996), activation oftranscription (Mollegaard et al., 1994), and directed mutagenesis(Faruqi et al., 1998). PNAs would provide a general and potent strategyfor probing the structure and function of chromosomal DNA in livingsystems if their remarkable strand invasion abilities could beefficiently applied inside cells.

Strand invasion by PNAs in cell-free systems is most potent at sequencesthat are partially single-stranded (Bertin and Nielsen, 1996; Zhang etal., 2000). Assembly of RNA polymerase and transcription factors intothe pre-initiation complex on DNA induces the formation of a structureknown as the open complex that contains several bases of single-strandedDNA (Holstege et al., 1997; Kahl et al., 2000). The exceptional abilityof PNAs to recognize duplex DNA allows them to intercept the opencomplex of an actively transcribed gene without a requirement forpreincubation. The open complex is formed during transcription of allgenes and PNAs can be synthesized to target any transcription initiationsite. Therefore, antigene PNAs that target an open complex at a promoterregion within chromosomal DNA would have the potential to be generaltools for controlling transcription initiation inside cells.

Inhibition of translation and bacterial growth by PNAs targeted toribosomal RNA was demonstrated by Good & Nielsen (1998). RNA guaninequadruplex invasion with complementary and homologous PNA probes hasbeen reported by Marin & Armitage (2005).

A locked nucleic acid (LNA), often referred to as inaccessible RNA, is amodified RNA nucleotide. The ribose moiety of an LNA nucleotide ismodified with an extra bridge connecting the 2′ and 4′ carbons. Thebridge “locks” the ribose in the 3′-endo structural conformation, whichis often found in the A-form of DNA or RNA. LNA nucleotides can be mixedwith DNA or RNA bases in the oligonucleotide whenever desired. Sucholigomers are commercially available. The locked ribose conformationenhances base stacking and backbone pre-organization. This significantlyincreases the thermal stability (melting temperature) ofoligonucleotides (Kaur et al., 2006).

LNA nucleotides are used to increase the sensitivity and specificity ofexpression in DNA microarrays, FISH probes, real-time PCR probes andother molecular biology techniques based on oligonucleotides. For the insitu detection of miRNA, the use of LNA was as of 2005 the onlyefficient method. A triplet of LNA nucleotides surrounding a single-basemismatch site maximizes LNA probe specificity unless the probe containsthe guanine base of G-T mismatch (You et al., 2006).

Other oligonucleotide modifications can be made to produce NAAs. Forexample, stability against nuclease degradation has been achieved byintroducing a phosphorothioate (P=S) backbone linkage at the 3′ end forexonuclease resistance and 2′ modifications (2′-OMe, 2′-F and related)for endonuclease resistance (WO 2005115481; Li et al., 2005; Choung etal., 2006). A motif having entirely of 2′-O-methyl and 2′-fluoronucleotides has shown enhanced plasma stability and increased in vitropotency (Allerson et al., 2005). The incorporation of 2′-O-Me and2′-O-MOE does not have a notable effect on activity (Prakash et al.,2005).

Sequences containing a 4′-thioribose modification have been shown tohave a stability 600 times greater than that of natural RNA (Hoshika etal, 2004). Crystal structure studies reveal that 4′-thioriboses adoptconformations very similar to the C3′-endo pucker observed forunmodified sugars in the native duplex (Haeberli et al., 2005).Stretches of 4′-thio-RNA were well tolerated in both the guide andnonguide strands. However, optimization of both the number and theplacement of 4′-thioribonucleosides is necessary for maximal potency.

In the boranophosphate linkage, a non-bridging phosphodiester oxygen isreplaced by an isoelectronic borane (BH3-) moiety. BoranophosphatesiRNAs have been synthesized by enzymatic routes using T7 RNA polymeraseand a boranophosphatc ribonucleoside triphosphatc in the transcriptionreaction. Boranophosphatc siRNAs are more active than native siRNAs ifthe center of the guide strand is not modified, and they may be at leastten times more nuclease resistant than unmodified siRNAs (Hall et al.,2004; Hall et al., 2006).

Certain terminal conjugates have been reported to improve or directcellular uptake. For example, NAAs conjugated with cholesterol improvein vitro and in vivo cell permeation in liver cells (Rand et al., 2005).Soutschek et al. (2004) have reported on the use ofchemically-stabilized and cholesterol-conjugated siRNAs have markedlyimproved pharmacological properties in vitro and in vivo.Chemically-stabilized siRNAs with partial phosphorothioate backbone and2′-O-methyl sugar modifications on the sense and antisense strands(discussed above) showed significantly enhanced resistance towardsdegradation by exo- and endonucleases in serum and in tissuehomogenates, and the conjugation of cholesterol to the 3′ end of thesense strand of an NAA by means of a pyrrolidine linker does not resultin a significant loss of gene-silencing activity in cell culture. Thesestudy demonstrates that cholesterol conjugation significantly improvesin vivo pharmacological properties of NAAs.

LNA bases may be included in a DNA backbone, by they can also be in abackbone of LNA, 2′-O-methyl RNA, 2′-methoxyethyl RNA, or 2′-fluoro RNA.These molecules may utilize either a phosphodiester or phosphorothioatebackbone.

U.S. Patent Publication 2008/0015162, incorporated herein by reference,provide additional examples of nucleic acid analogs useful in thepresent invention. The following excerpts are derived from that documentand are exemplary in nature only:

In certain embodiments, oligomeric compounds comprise one or moremodified monomers, including 2′-modified sugars, such as BNA's andmonomers (e.g., nucleosides and nucleotides) with 2′-substituents suchas allyl, amino, azido, thio, O-allyl, O—C₁-C₁₀ alkyl, —OCF₃,O—(CH₂)₂——O—CH₃, 2′—O(CH₂)₂SCH₃, O—(CH₂)₂—O—N(R_(m))(R_(n)), orO—CH₂—C(═O)——N(R_(m))(R_(n)), where each R_(m) and R_(n) is,independently, H or substituted or unsubstituted C₁-C₁₀ alkyl.

In certain embodiments, the oligomeric compounds including, but nolimited to short antisense compounds of the present invention, compriseone or more high affinity monomers provided that the oligomeric compounddoes not comprise a nucleotide comprising a 2′-O(CH₂)_(n)H, wherein n isone to six. In certain embodiments, the oligomeric compounds including,but no limited to short antisense compounds of the present invention,comprise one or more high affinity monomer provided that the oligomericcompound does not comprise a nucleotide comprising a 2′-OCH₃ or a2′-O(CH₂)₂OCH₃. In certain embodiments, the oligomeric compoundsincluding, but no limited to short antisense compounds of the presentinvention, comprise one or more high affinity monomer provided that theoligomeric compound does not comprise a .alpha.-L-Methyleneoxy(4′-CH₂—-O—2′) BNA. In certain embodiments, the oligomeric compoundsincluding, but no limited to short antisense compounds of the presentinvention, comprise one or more high affinity monomer provided that theoligomeric compound does not comprise a β-D-Methyleneoxy (4′-CH₂—-O—2′)BNA. In certain embodiments, the oligomeric compounds including, but nolimited to short antisense compounds of the present invention, compriseone or more high affinity monomer provided that the oligomeric compounddoes not comprise a α-L-Methyleneoxy (4′-CH₂—O—2′) BNA or aβ-D-Methyleneoxy (4′-CH₂—O—2′) BNA.

The naturally occurring base portion of a nucleoside is typically aheterocyclic base. The two most common classes of such heterocyclicbases are the purines and the pyrimidines. For those nucleosides thatinclude a pentofuranosyl sugar, a phosphate group can be linked to the2′, 3′ or 5′ hydroxyl moiety of the sugar. In forming oligonucleotides,those phosphate groups covalently link adjacent nucleosides to oneanother to form a linear polymeric compound. Within oligonucleotides,the phosphate groups are commonly referred to as forming theinternucleotide backbone of the oligonucleotide. The naturally occurringlinkage or backbone of RNA and of DNA is a 3′ to 5′ phosphodiesterlinkage.

In addition to “unmodified” or “natural” nucleobases such as the purinenucleobases adenine (A) and guanine (G), and the pyrimidine nucleobasesthymine (T), cytosine (C) and uracil (U), many modified nucleobases ornucleobase mimetics known to those skilled in the art are amenable withthe compounds described herein. In certain embodiments, a modifiednucleobase is a nucleobase that is fairly similar in structure to theparent nucleobase, such as for example a 7-deaza purine, a 5-methylcytosine, or a G-clamp. In certain embodiments, nucleobase mimeticinclude more complicated structures, such as for example a tricyclicphenoxazine nucleobase mimetic. Methods for preparation of the abovenoted modified nucleobases are well known to those skilled in the art.

Oligomeric compounds provided herein may comprise one or more monomer,including a nucleoside or nucleotide, having a modified sugar moiety.For example, the furanosyl sugar ring of a nucleoside can be modified ina number of ways including, but not limited to, addition of asubstituent group, bridging of two non-geminal ring atoms to form abicyclic nucleic acid (BNA).

In certain embodiments, oligomeric compounds comprise one or moremonomers that is a BNA. In certain such embodiments, BNAs include, butare not limited to, (A) α-L-Methyleneoxy (4′-CH₂—O-2′) BNA, (B)β-D-Methyleneoxy (4′-CH₂—O-2′) BNA, (C) Ethyleneoxy (4′-(CH₂)₂—O-2′)BNA, (D) Aminooxy (4′-CH₂—O—N(R)-2′) BNA and (E) Oxyamino(4′-CH₂—N(R)—O-2′) BNA.

In certain embodiments, BNA compounds include, but are not limited to,compounds having at least one bridge between the 4′ and the 2′ positionof the sugar wherein each of the bridges independently comprises 1 orfrom 2 to 4 linked groups independently selected from —[C(R₁)(R₂)]_(n)—,—C(R₁)═C(R₂)—, —C(R₁)═N—, —C(═NR₁)—, —C(═O)—, —C(═S)—, —S(═O)_(x)— and—N(R₁)—; wherein: x is 0, 1, or 2; n is 1, 2, 3, or 4; each R₁ and R₂is, independently, H, a protecting group, hydroxyl, C₁-C₁₂ alkyl,substituted C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, substituted C₂-C₁₂ alkenyl,C₂-C₁₂ alkynyl, substituted C₂-C₁₂ alkynyl, C₅-C₂₀ aryl, substitutedC₅-C₂₀ aryl, heterocycle radical, substituted heterocycle radical,heteroaryl, substituted heteroaryl, C₅-C₇ alicyclic radical, substitutedC₅-C₇ alicyclic radical, halogen, OJ₁, NJ₁J₂, SJ₁, N₃, COOJ₁, acyl(C(═O)—H), substituted acyl, CN, sulfonyl (S(═O)₂-J₁), or sulfoxyl(S(═O)-J₁); and each J₁ and J₂ is, independently, H, C₁-C₁₂ alkyl,substituted C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, substituted C₂-C₁₂ alkenyl,C₂-C₁₂ alkynyl, substituted C₂-C₁₂ alkynyl, C₅-C₂₀ aryl; substitutedC₅-C₂₀ aryl, acyl (C(═O)—H), substituted acyl, a heterocycle radical, asubstituted heterocycle radical, C₁-C₁₂ aminoalkyl, substituted C₁-C₁₂aminoalkyl or a protecting group.

In one embodiment, each of the bridges of the BNA compounds is,independently, —[C(R₁)(R₂)]_(n)—, —C(R₁R₂)—N(R₁)—O— or—C(R₁R₂)—O—N(R₁)—. In another embodiment, each of said bridges is,independently, 4′-CH₂-2′, 4′-(CH₂)₂-2′, 4′-(CH₂)₃-2′, 4′-CH₂—O-2′,4′-(CH₂)₂—O-2′, 4′- CH₂—O—N(R₁)-2′ and 4′-CH₂—N(R₁)—O-2′— wherein eachR₁ is, independently, H, a protecting group or C₁-C₁₂ alkyl.

Certain BNA's have been prepared and disclosed in the patent literatureas well as in scientific literature (Singh et al., 1998; Koshkin et al.,1998; Wahlestedt et al., 2000; Kumar et al., 1998; WO 94/14226; WO2005/021570; Singh et al., 1998. Examples of issued US patents andpublished applications that disclose BNA s include, for example, U.S.Pat. Nos. 7,053,207; 6,268,490; 6,770,748; 6,794,499; 7,034,133; and6,525,191; and U.S. Patent Publication Nos. 2004/0171570; 2004/0219565;2004/0014959; 2003/0207841; 2004/0143114; and 2003/0082807.

Also provided herein are BNAs in which the 2′-hydroxyl group of theribosyl sugar ring is linked to the 4′ carbon atom of the sugar ringthereby forming a methyleneoxy (4′-CH₂—O-2′) linkage to form thebicyclic sugar moiety (reviewed in Elayadi et al., 2001; Braasch et al.,2001; and Orum et al., 2001; see also U.S. Pat. Nos. 6,268,490 and6,670,461). The linkage can be a methylene (—CH₂—) group bridging the 2′oxygen atom and the 4′ carbon atom, for which the term methyleneoxy(4′-CH₂—O-2′) BNA is used for the bicyclic moiety; in the case of anethylene group in this position, the term ethyleneoxy (4′-CH₂CH₂—O-2′)BNA is used (Singh et al., 1998; Morita et al., 2003). Methyleneoxy(4′-CH₂—O-2′) BNA and other bicyclic sugar analogs display very highduplex thermal stabilities with complementary DNA and RNA (Tm=+3 to +10°C.), stability towards 3′-exonucleolytic degradation and good solubilityproperties. Potent and nontoxic antisense oligonucleotides comprisingBNAs have been described (Wahlestedt et al., 2000).

An isomer of methyleneoxy (4′-CH₂—O-2′) BNA that has also been discussedis α-L-methyleneoxy (4′-CH₂—O-2′) BNA which has been shown to havesuperior stability against a 3′-exonuclease. The α-L-methyleneoxy(4′-CH₂—O-2′) BNA's were incorporated into antisense gapmers andchimeras that showed potent antisense activity (Frieden et al., 2003).

The synthesis and preparation of the methyleneoxy (4′-CH₂—O-2′) BNAmonomers adenine, cytosine, guanine, 5-methyl-cytosine, thymine anduracil, along with their oligomerization, and nucleic acid recognitionproperties have been described (Koshkin et al., 1998). BNAs andpreparation thereof are also described in WO 98/39352 and WO 99/14226.

Analogs of methyleneoxy (4′-CH₂—O-2′) BNA, phosphorothioate-methyleneoxy(4′-CH₂—O-2′) BNA and 2′-thio-BNAs, have also been prepared (Kumar etal., 1998). Preparation of locked nucleoside analogs comprisingoligodeoxyribonucleotide duplexes as substrates for nucleic acidpolymerases has also been described (Wengel et al., WO 99/14226).Furthermore, synthesis of 2′-amino-BNA, a novel comformationallyrestricted high-affinity oligonucleotide analog has been described inthe art (Singh et al., 1998). In addition, 2′-amino- and2′-methylamino-BNA's have been prepared and the thermal stability oftheir duplexes with complementary RNA and DNA strands has beenpreviously reported.

Modified sugar moieties are well known and can be used to alter,typically increase, the affinity of the antisense compound for itstarget and/or increase nuclease resistance. A representative list ofpreferred modified sugars includes but is not limited to bicyclicmodified sugars (BNA's), including methyleneoxy (4′-CH₂—O-2′) BNA andethyleneoxy (4′-(CH₂)₂—O-2′ bridge) BNA; substituted sugars, especially2′-substituted sugars having a 2′-F, 2′-OCH₃ or a 2′-O(CH₂)₂—OCH₃substituent group; and 4′-thio modified sugars. Sugars can also bereplaced with sugar mimetic groups among others. Methods for thepreparations of modified sugars are well known to those skilled in theart. Some representative patents and publications that teach thepreparation of such modified sugars include, but are not limited to,U.S. Pat. Nos. 4,981,957; 5,118,800; 5,319,080; 5,359,044; 5,393,878;5,446,137; 5,466,786; 5,514,785; 5,519,134; 5,567,811; 5,576,427;5,591,722; 5,597,909; 5,610,300; 5,627,053; 5,639,873; 5,646,265;5,658,873; 5,670,633; 5,792,747; 5,700,920; 6,531,584; and 6,600,032;and WO 2005/121371.

In one embodiment, each of the substituted groups, is, independently,mono- or poly-substituted with optionally protected substituent groupsindependently selected from halogen, oxo, hydroxyl, OJ₁, NJ₁J₂, SJ₁, N₃,OC(═X)J₁, OC(═X)NJ₁J₂, NJ₃C(═X)NJ₁J₂ and CN, wherein each J₁, J₂ and J₃is, independently, H or C₁-C₆ alkyl, and X is O, S or NJ₁.

In certain such embodiments, each of the substituted groups, is,independently, mono or poly substituted with substituent groupsindependently selected from halogen, oxo, hydroxyl, OJ₁, NJ₁J₂, SJ₁, N₃,OC(═X)J₁, and NJ₃C(═X)NJ₁J₂, wherein each J₁, J₂ and J₃ is,independently, H, C₁-C₆ alkyl, or substituted C₁-C₆ alkyl and X is O orNJ₁.

In one embodiment, each of the substituted groups, is, independently,mono or poly substituted with optionally protected substituent groupsindependently selected from halogen, oxo, hydroxyl, OJ₁, NJ₁J₂, SJ₁, N₃,OC(═X)J₁, OC(═X)NJ₁J₂, NJ₃C(═X)NJ₁J₂ and CN, wherein each J₁, J₂ and J₃is, independently, H or C₁-C₆ alkyl, and X is O, S or NJ₁.

In one embodiment, each of the substituted groups, is, independently,mono- or poly-substituted with substituent groups independently selectedfrom halogen, oxo, hydroxyl, OJ₁, NJ₁J₂, SJ₁, N₃, OC(═X)J₁, andNJ₃C(═X)NJ₁J₂, wherein each J₁, J₂ and J₃ is, independently, H or C₁-C₆alkyl, and X is O or NJ₁.

In certain embodiments, monomers include sugar mimetics. In certain suchembodiments, a mimetic is used in place of the sugar orsugar-internucleoside linkage combination, and the nucleobase ismaintained for hybridization to a selected target. Representativeexamples of a sugar mimetics include, but are not limited to,cyclohexenyl or morpholino. Representative examples of a mimetic for asugar-internucleoside linkage combination include, but are not limitedto, peptide nucleic acids (PNA) and morpholino groups linked byuncharged achiral linkages. In some instances a mimetic is used in placeof the nucleobase. Representative nucleobase mimetics are well known inthe art and include, but are not limited to, tricyclic phenoxazineanalogs and universal bases (Berger et al., 2000, incorporated herein byreference). Methods of synthesis of sugar, nucleoside and nucleobasemimetics are well known to those skilled in the art.

Described herein are linking groups that link monomers (including, butnot limited to, modified and unmodified nucleosides and nucleotides)together, thereby forming an oligomeric compound. The two main classesof linking groups are defined by the presence or absence of a phosphorusatom. Representative phosphorus containing linkages include, but are notlimited to, phosphodiesters (P═O), phosphotriesters, methylphosphonates,phosphoramidate, and phosphorothioates (P=S). Representativenon-phosphorus containing linking groups include, but are not limitedto, methylenemethylimino (—CH₂—N(CH₃)—O—CH₂—), thiodiester C(O)—S—),thionocarbamate (—O—C(O)(NH)—S—); siloxane and N,N′-dimethylhydrazine(—CH₂—N(CH₃)—N(CH₃)—). Oligomeric compounds having non-phosphoruslinking groups are referred to as oligonucleosides. Modified linkages,compared to natural phosphodiester linkages, can be used to alter,typically increase, nuclease resistance of the oligomeric compound. Incertain embodiments, linkages having a chiral atom can be prepared aracemic mixtures, as separate enantiomers. Representative chirallinkages include, but are not limited to, alkylphosphonates andphosphorothioates. Methods of preparation of phosphorous-containing andnon-phosphorous-containing linkages are well known to those skilled inthe art.

The oligomeric compounds described herein contain one or more asymmetriccenters and thus give rise to enantiomers, diastereomers, and otherstereoisomeric configurations that may be defined, in terms of absolutestereochemistry, as (R) or (S), α or β such as for sugar anomers, or as(D) or (L) such as for amino acids et al. Included in the antisensecompounds provided herein are all such possible isomers, as well astheir racemic and optically pure forms.

In certain embodiments, provided herein are oligomeric compounds havingreactive phosphorus groups useful for forming linkages including forexample phosphodiester and phosphorothioate internucleoside linkages.Methods of preparation and/or purification of precursors or oligomericcompounds are not a limitation of the compositions or methods providedherein. Methods for synthesis and purification of oligomeric compoundsincluding DNA, RNA, oligonucleotides, oligonucleosides, and antisensecompounds are well known to those skilled in the art.

Generally, oligomeric compounds comprise a plurality of monomericsubunits linked together by linking groups. Nonlimiting examples ofoligomeric compounds include primers, probes, antisense compounds,antisense oligonucleotides, external guide sequence (EGS)oligonucleotides, alternate splicers, and siRNAs. As such, thesecompounds can be introduced in the form of single-stranded,double-stranded, circular, branched or hairpins and can containstructural elements such as internal or terminal bulges or loops.Oligomeric double-stranded compounds can be two strands hybridized toform double-stranded compounds or a single strand with sufficient selfcomplementarity to allow for hybridization and formation of a fully orpartially double-stranded compound.

In certain embodiments, the present invention provides chimericoligomeric compounds. In certain such embodiments, chimeric oligomericcompounds are chimeric oligonucleotides. In certain such embodiments,the chimeric oligonucleotides comprise differently modified nucleotides.In certain embodiments, chimeric oligonucleotides are mixed-backboneantisense oligonucleotides. In general, a chimeric oligomeric compoundwill have modified nucleosides that can be in isolated positions orgrouped together in regions that will define a particular motif. Anycombination of modifications and/or mimetic groups can comprise achimeric oligomeric compound as described herein. In certainembodiments, chimeric oligomeric compounds typically comprise at leastone region modified so as to confer increased resistance to nucleasedegradation, increased cellular uptake, and/or increased bindingaffinity for the target nucleic acid. In certain embodiments, anadditional region of the oligomeric compound may serve as a substratefor enzymes capable of cleaving RNA:DNA or RNA:RNA hybrids. By way ofexample, RNase H is a cellular endonuclease that cleaves the RNA strandof an RNA:DNA duplex. Activation of RNase H, therefore, results incleavage of the RNA target, thereby greatly enhancing the efficiency ofinhibition of gene expression. Consequently, comparable results canoften be obtained with shorter oligomeric compounds when chimeras areused, compared to for example phosphorothioate deoxyoligonucleotideshybridizing to the same target region. Cleavage of the RNA target can beroutinely detected by gel electrophoresis and, if necessary, associatednucleic acid hybridization techniques known in the art.

B. Design Considerations

The present invention contemplates the production of inhibitory NAAstargeting CAG repeats of various disease-related genes and messages. Ingeneral, the NAAs will comprise a single-stranded analog of about 7-30bases that binds to a CAG/CUG repeat, or to both a repeat and portion ofa region flanking a CAG/CUG repeat, defined as “a repeat junction.” Thelength may be 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29 or 30 bases in length. In addition,nucleic acid analog can be designed to lack bases that recruit RNAseH.

III. Treatment of Repeat-Associated Diseases

The present invention also involves the treatment of polyglutamineneurodegenerative diseases, discussed above. By treatment, it is notnecessary that all symptoms of the disease be addressed, or that anydegree of “cure” be achieved. Rather, to accomplish a meaningfultreatment, all that is required is that one or more symptoms of thedisease be ameliorated to some degree, an advantageous effect beprovided in combination with another therapy, or that the diseaseprogression be slowed.

Where clinical applications are contemplated, it will be necessary toprepare pharmaceutical compositions in a form appropriate for theintended application. Generally, this will entail preparing compositionsthat are essentially free of pyrogens, as well as other impurities thatcould be harmful to humans or animals. One will generally desire toemploy appropriate salts, buffers, and lipids to render delivery of theoligonucleotides to allow for uptake by target cells. Such methods ancompositions are well known in the art, for example, as disclosed inU.S. Pat. Nos. 6,747,014 and 6,753,423. Compositions of the presentinvention comprise an effective amount of the oligonucleotide to cells,dissolved or dispersed in a pharmaceutically acceptable carrier ormedium.

The phrase “pharmaceutically or pharmacologically acceptable” refer tomolecular entities and compositions that do not produce adverse,allergic, or other untoward reactions when administered to an animal ora human. As used herein, “pharmaceutically acceptable carrier” includesany and all solvents, dispersion media, coatings, antibacterial andantifungal agents, isotonic and absorption delaying agents, liposomes,cationic lipid formulations, microbubble nanoparticles, and the like.The use of such media and agents for pharmaceutically active substancesis well-known in the art. I'm not so sure this is true. Delivery is amajor issue in the field. Except insofar as any conventional media oragent is incompatible with the vectors or cells of the presentinvention, its use in therapeutic compositions is contemplated.Supplementary active ingredients also can be incorporated into thecompositions.

The active compositions of the present invention may include classicpharmaceutical preparations. Administration of these compositionsaccording to the present invention will be via any common route so longas the target tissue is available via that route. This includes oral,nasal, buccal, or topical. Alternatively, administration may be byintradermal, subcutaneous, intramuscular, intraperitoneal or intravenousinjection, or introduction into the CNS, such as into spinal fluid. Suchcompositions would normally be administered as pharmaceuticallyacceptable compositions, described supra.

The pharmaceutical forms suitable for injectable use include sterileaqueous solutions or dispersions and sterile powders for theextemporaneous preparation of sterile injectable solutions ordispersions. In all cases the form must be sterile and must be fluid tothe extent that easy syringability exists. It must be stable under theconditions of manufacture and storage and must be preserved against thecontaminating action of microorganisms, such as bacteria and fungi. Thecarrier can be a solvent or dispersion medium containing, for example,water, ethanol, polyol (for example, glycerol, propylene glycol, andliquid polyethylene glycol, and the like), suitable mixtures thereof,and vegetable oils. The proper fluidity can be maintained, for example,by the use of a coating, such as lecithin, by the maintenance of therequired particle size in the case of dispersion and by the use ofsurfactants. The prevention of the action of microorganisms can bebrought about by various antibacterial an antifungal agents, forexample, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, andthe like. In many cases, it will be preferable to include isotonicagents, for example, sugars or sodium chloride. Prolonged absorption ofthe injectable compositions can be brought about by the use in thecompositions of agents delaying absorption, for example, aluminummonostearate and gelatin.

Sterile injectable solutions are prepared by incorporating the activecompounds in the required amount in the appropriate solvent with variousof the other ingredients enumerated above, as required, followed byfiltered sterilization. Generally, dispersions are prepared byincorporating the various sterilized active ingredients into a sterilevehicle which contains the basic dispersion medium and the requiredother ingredients from those enumerated above. In the case of sterilepowders for the preparation of sterile injectable solutions, thepreferred methods of preparation are vacuum-drying and freeze-dryingtechniques which yield a powder of the active ingredient plus anyadditional desired ingredient from a previously sterile-filteredsolution thereof.

As used herein, “pharmaceutically acceptable carrier” includes any andall solvents, lipids, nanoparticles, dispersion media, coatings,antibacterial and antifungal agents, isotonic and absorption delayingagents and the like. The use of such media and agents for pharmaceuticalactive substances is well known in the art. Except insofar as anyconventional media or agent is incompatible with the active ingredient,its use in the therapeutic compositions is contemplated. Supplementaryactive ingredients can also be incorporated into the compositions.

For oral administration the NAAs of the present invention may beincorporated with excipients. The compositions of the present inventionmay be formulated in a neutral or salt form. Pharmaceutically-acceptablesalts include the acid addition salts (formed with the free amino groupsof the protein) and which are formed with inorganic acids such as, forexample, hydrochloric or phosphoric acids, or such organic acids asacetic, oxalic, tartaric, mandelic, and the like. Salts formed with thefree carboxyl groups can also be derived from inorganic bases such as,for example, sodium, potassium, ammonium, calcium, or ferric hydroxides,and such organic bases as isopropylaminc, trimethylamine, histidine,procaine and the like.

Upon formulation, solutions will be administered in a manner compatiblewith the dosage formulation and in such amount as is therapeuticallyeffective. The formulations are easily administered in a variety ofdosage forms such as injectable solutions, drug release capsules and thelike. For parenteral administration in an aqueous solution, for example,the solution should be suitably buffered if necessary and the liquiddiluent first rendered isotonic with sufficient saline or glucose. Theseparticular aqueous solutions are especially suitable for intravenous,intramuscular, subcutaneous and intraperitoneal administration. In thisconnection, sterile aqueous media which can be employed will be known tothose of skill in the art in light of the present disclosure. Forexample, one dosage could be dissolved in 1 ml of isotonic NaCl solutionand either added to 1000 ml of hypodermoclysis fluid or injected at theproposed site of infusion, (see for example, “Remington's PharmaceuticalSciences” 15th Edition, pages 1035-1038 and 1570-1580). Some variationin dosage will necessarily occur depending on the condition of thesubject being treated. The person responsible for administration will,in any event, determine the appropriate dose for the individual subject.Moreover, for human administration, preparations should meet sterility,pyrogenicity, general safety and purity standards as required by FDAOffice of Biologics standards.

Of particular interest to the present invention is the use of lipiddelivery vehicles. Lipid vehicles encompass micelles, microemulsions,macroemulsions, liposomes, and similar carriers. The term micellesrefers to colloidal aggregates of amphipathic (surfactant) moleculesthat are formed at a well-defined concentration known as the criticalmicelle concentration. Micelles are oriented with the nonpolar portionsat the interior and the polar portions at the exterior surface, exposedto water. The typical number of aggregated molecules in a micelle(aggregation number) is 50 to 100. Microemulsions are essentiallyswollen micelles, although not all micellar solutions can be swollen toform microemulsions. Microemulsions are thermodynamically stable, areformed spontaneously, and contain particles that are extremely small.Droplet diameters in microemulsions typically range from 10 100 nm. Incontrast, the term macroemulsions refers to droplets with diametersgreater than 100 nm. Liposomes are closed lipid vesicles comprisinglipid bilayers that encircle aqueous interiors. Liposomes typically havediameters of 25 nm to 1 μm (see, e.g., Shah, 1998; Janoff, 1999).

In one embodiment of a liposome formulation, the principal lipid of thevehicle may be phosphatidylcholine. Other useful lipids include variousnatural (e.g., tissue derived L-α-phosphatidyl: egg yolk, heart, brain,liver, soybean) and/or synthetic (e.g., saturated and unsaturated1,2-diacyl-SN-glycero-3-phosphocholines,1-acyl-2-acyl-SN-glycero-3-phosphocholines,1,2-diheptanoyl-SN-glycero-3-phosphocholine) derivatives of the same.Such lipids can be used alone, or in combination with a secondary lipid.Such secondary helper lipids may be non-ionic or uncharged atphysiological pH, including non-ionic lipids such as cholesterol andDOPE (1,2-dioleolylglyceryl phosphatidylethanolamine). The molar ratioof a phospholipid to helper lipid can range from about 3:1 to about 1:1,from about 1.5:1 to about 1:1, and about 1:1.

Another specific lipid formulation comprises the SNALP formulation,containing the lipids 3-N-[(ω methoxypoly(ethyleneglycol)₂₀₀₀)carbamoyl]-1,2-dimyristyloxy-propylamine(PEG-C-DMA),1,2-dilinoleyloxy-N,N-dimethyl-3-aminopropane (DLinDMA),1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol, in a2:40:10:48 molar % ratio. See Zimmerman et al. (2006).

A liposome is, in simplest form, composed of two lipid layers. The lipidlayer may be a monolayer, or may be multilamellar and include multiplelayers. Constituents of the liposome may include, for example,phosphatidylcholine, cholesterol, phosphatidylethanolamine, etc.Phosphatidic acid, which imparts an electric charge, may also be added.Exemplary amounts of these constituents used for the production of theliposome include, for instance, 0.3 to 1 mol, 0.4 to 0.6 mol ofcholesterol; 0.01 to 0.2 mol, 0.02 to 0.1 mol ofphosphatidylethanolamine; 0.0 to 0.4 mol, or O-0.15 mol of phosphatidicacid per 1 mol of phosphatidylcholine.

Liposomes can be constructed by well-known techniques (see, e.g.,Gregoriadis (1993). Lipids are typically dissolved in chloroform andspread in a thin film over the surface of a tube or flask by rotaryevaporation. If liposomes comprised of a mixture of lipids are desired,the individual components are mixed in the original chloroform solution.After the organic solvent has been eliminated, a phase consisting ofwater optionally containing buffer and/or electrolyte is added and thevessel agitated to suspend the lipid. Optionally, the suspension is thensubjected to ultrasound, either in an ultrasonic bath or with a probesonicator, until the particles are reduced in size and the suspension isof the desired clarity. For transfection, the aqueous phase is typicallydistilled water and the suspension is sonicated until nearly clear,which requires several minutes depending upon conditions, kind, andquality of the sonicator. Commonly, lipid concentrations are 1 mg/ml ofaqueous phase, but could be higher or lower by about a factor of ten.

Lipids, from which the solvents have been removed, can be emulsified bythe use of a homogenizer, lyophilized, and melted to obtainmultilamellar liposomes. Alternatively, unilamellar liposomes can beproduced by the reverse phase evaporation method (Szoka andPapahadjopoulos, 1978). Unilamellar vesicles can also be prepared bysonication or extrusion. Sonication is generally performed with abath-type sonifier, such as a Branson tip sonifier (G. HeinemannUltrashall and Labortechnik, Schwabisch Gmund, Germany) at a controlledtemperature as determined by the melting point of the lipid. Extrusionmay be carried out by biomembrane extruders, such as the LipexBiomembrane Extruder (Northern Lipids Inc, Vancouver, British Columbia,Canada). Defined pore size in the extrusion filters may generateunilamellar liposomal vesicles of specific sizes. The liposomes can alsobe formed by extrusion through an asymmetric ceramic filter, such as aCeraflow Microfilter (commercially available from the Norton Company,Worcester, Mass.).

Following liposome preparation, the liposomes that have not been sizedduring formation may be sized by extrusion to achieve a desired sizerange and relatively narrow distribution of liposome sizes. A size rangeof about 0.2-0.4 microns will allow the liposome suspension to besterilized by filtration through a conventional filter (e.g., a 0.22micron filter). The filter sterilization method can be carried out on ahigh throughput basis.

Several techniques are available for sizing liposomes to a desired size,including, ultrasonication, high-speed homogenization, and pressurefiltration (Hope et al., 1985; U.S. Pat. Nos. 4,529,561 and 4,737,323).Sonicating a liposome suspension either by bath or probe sonicationproduces a progressive size reduction down to small unilamellar vesiclesless than about 0.05 microns in size. Multilamellar vesicles can berecirculated through a standard emulsion homogenizer until selectedliposome sizes, typically between about 0.1 and 0.5 microns. The size ofthe liposomal vesicles may be determined by quasi-elastic lightscattering (QELS) (see Bloomfield, 1981). Average liposome diameter maybe reduced by sonication of formed liposomes. Intermittent sonicationcycles may be alternated with QELS assessment to guide efficientliposome synthesis.

Liposomes can be extruded through a small-pore polycarbonatc membrane oran asymmetric ceramic membrane to yield a well-defined sizedistribution. Typically, a suspension is cycled through the membrane oneor more times until the desired liposome size distribution is achieved.The liposomes may be extruded through successively smaller-poremembranes, to achieve a gradual reduction in liposome size. For use inthe present invention, liposomes have a size of about 0.05 microns toabout 0.5 microns, or having a size of about 0.05 to about 0.2 microns.

IV. EXAMPLES

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples which follow representtechniques discovered by the inventor to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

Example 1 Materials & Methods

Oligonucleotides and PNAs. PNA-peptide conjugates were synthesized on anExpedite 8909 synthesizer (Applied Biosystems, Foster City, Calif.)using reagents obtained from Applied Biosystems (Mayfield et al., 1999;Janowski et al., 2006). PNA-peptide conjugates were purified by C-18reversed phase HPLC and assayed by mass spectrometry (Mayfield et al.,1999; Janowski et al., 2006). LNA oligonucleotides were provided bySigma-Proligo (Paris, France). siRNAs were purchased from Integrated DNATechnologies (IDT, Coralville, Iowa).

Cell Culture and Transfection. Patient-derived fibroblast cell linesGM04281 and GM06151 were obtained from the Coriell Institute (Camden,N.J.). Cells were maintained at 37° C. and 5% CO₂ in Minimal EssentialMedia Eagle (MEM) (Sigma, M4655) supplemented with 10% heat inactivatedfetal bovine serum (Sigma) and 0.5% MEM nonessential amino acids(Sigma). Cells were plated in E-well plates at 60,000 cells/well insupplemented MEM two days prior to transfection. Stock solutions ofPNA-peptide conjugates were heated at 65° C. for 5 min before use todissolve any aggregates that may have formed. PNA-peptide conjugateswere diluted to the appropriate concentration using OptiMEM (Invitrogen,Carlsbad, Calif.) and then added to cells. After 24 h, the mediacontaining PNA-peptides were removed and replaced by fresh supplementedMEM. Cells were typically harvested 4 days after transfection forprotein assay. siRNAs or LNAs were transfected to cells using RNAiMAX(Invitrogen) according to the manufacturer's instructions. Theappropriate amount of the lipid (3 μL, for 100 nM oligonucleotides) wereadded to OptiMEM containing oligonucleotides and theoligonucleotide-lipid mixture (250 μL) were incubated for 20 min.OptiMEM was added to the mixture to a final volume of 1.25 mL and thenadded to cells. The media were exchanged 24 h later with freshsupplemented MEM.

Analysis of Huntingtin Expression. Cells were harvested withtrypsin-EDTA solution (Invitrogen). The protein concentration in eachsample was quantified with BCA assay (Thermo Scientific, Waltham,Mass.). SDS-PAGE (separating gel: 5% acrylamide-bisacrylamide/34.7:1,450 mM Tris-acetate pH 8.8; stacking gel: 4%acrylamide-bisacrylamide/34.7:1, 150 mM Tris-acetate pH 6.8) (XT TricineRunning Buffer, Bio-rad, Hercules, Calif.) was used to separatewild-type and mutant HTT proteins. Gels were run at 70V for 15 minfollowed by 100V for 4 h. The electrophoresis apparatus was placed inice-water bath to prevent overheating of the running buffer. Theinventors monitored expression of actin protein to ensure even loadingon protein in each lane.

In parallel with analysis for HTT expression, portions of each proteinlysate sample were analyzed for actin expression by SDS-PAGE (7.5%acrylamide pre-cast gels; Bio-Rad). These gels were run at 70V for 15min followed by 100V for 1 h. After gel electrophoresis, proteins weretransferred to membrane (Hybond-C Extra; GE Healthcare Bio-Sciences,Piscataway, N.J.). Primary antibodies specific for each protein wereobtained and used at the indicated dilution ratio: anti-huntingtinantibody (MAB2166; 1:10000; Chemicon, CA), anti-β-actin antibody(1:10000; Sigma).

HRP conjugate anti-mouse or anti-rabbit secondary antibody (1:10000 and1:5000, respectively; Jackson ImmunoResearch Laboratories, West Grove,Pa.) was used for visualizing proteins by SuperSignal West PicoChemiluminescent Substrate (Thermo Scientific). Protein bands werequantified using ImageJ (Rasband, W. S ImageJ, U. S. National Institutesof Health, Bethesda, Md., USA, rsb.info.nih.gov/ij/, 1997-2007). Thepercentage of inhibition was calculated as a relative value to a controlsample.

Analysis of TBP, AAK1, and POU3F2. The number of CAG repeats wasestimated according to the published mRNA sequence in GeneBank. TATA boxbinding protein (TBP) (˜19 CAG repeats, NM_003194), AAK1 (6 CAG repeats,NM_014911), and POU3F2 (˜6 CAG repeats, NM_005604). Protein lysates wereanalyzed by SDS-PAGE (7.5% acrylamide pre-cast gels; Bio-Rad). anti-TBPantibody (1:2000; Sigma), anti-AAK1 antibody (1:1000; Abcam, CambridgeMass.), anti-POU3F2 antibody (1:1000; Abnova, Taipei, Taiwan).

Neuronal Cells Assay (Slow et al., 2003; Tang et al., 2005). YAC128 mice(FVBN/NJ background strain) were obtained from Jackson Labs (stocknumber 004938). The male YAC128 mice were crossed to wild-type (WT)female FVBN/NJ mice and P1-P2 pups were collected and genotyped by PCR.The primary cultures of striatal medium spiny neurons (MSN) wereestablished from YAC128 and control wild-type pups. Striata weredissected, diced and digested with trypsin. After dissociation, neuronswere plated on poly-L-lysine (Sigma) coated 12 mm round coverslips(Assistent) in Neurobasal-A medium supplemented with 2% B27, 1 mMglutamine and penicillin-streptomycin (all from Invitrogen) and kept at37° C. in a 5% CO₂ environment. PNA was added to the 9-DIV (days invitro) MSN. The 13-DIV MSN were exposed for 7 h to 250 μM glutamate inNeurobasal-A added to the culture medium. Immediately after thetreatment with glutamate, neurons were fixed for 30 min in 4%paraformaldehyde plus 4% sucrose in PBS (pH7.4), permeabilized for 5 minin 0.25% Triton-X-100, and stained by using the DeadEnd fluorometricTUNEL System (Promega). Nuclei were counterstained with 5 μM propidiumiodine (PI) (Molecular Probes). Coverslips were extensively washed withPBS and mounted in Mowiol 4-88 (Polysciences). For quantification six toeight randomly chosen microscopic fields containing 100-300 MSN eachwere cell-counted for YAC128 and wild-type cultures. The number ofTUNEL-positive neuronal nuclei was calculated as a fraction ofPI-positive neuronal nuclei in each microscopic field. The fractions ofTUNEL-positive nuclei determined for each microscopic field wereaveraged and the results are presented as means±SE (n=number of fieldscounted). MSN cells were supported in culture by surrounding glialcells, but only MSN cells were counted during the neuroprotection assay.

Analysis of HTT mRNA Level by Quantitative PCR. Total RNA from treatedand untreated fibroblast cells was extracted using TRIzol (Invitrogen) 3days after transfection. Each sample was then treated with DNase I at25° C. for 10 min. Reverse transcription reactions were done using HighCapacity Reverse Transcription Kit (Applied Biosystems) according to themanufacturer's protocol. Quantitative PCR was performed on a 7500real-time PCR system (Applied Biosystems) using iTaq SYBR Green Supermix(Bio-rad). Data was normalized relative to levels of GAPDH mRNA. Primersequences specific for HTT are as follows: forward primer,5′-CGACAGCAGTCAGTGATTG-3′; (SEQ ID NO:1) reverse primer,5′-ACCACTCTGGCTTCACAAGG-3′ (SEQ ID NO:2). Primers specific for GAPDH areobtained from Applied Biosystems.

Example 2 Results

The inventors hypothesized that it might be possible to achieveselectivity using single-stranded oligomers that discriminate amongdifferences in mRNA secondary structure rather than mRNA primarysequence. Computational prediction, NMR and footprinting assays indicatethat triplet repeat sequences within RNA form hairpin structures (FIG.1A) (Sobczak et al., 2003; Gacy et al., 1995). The structures formed bywild-type and mutant mRNAs will possess different energies andstabilities, possibly enabling selective recognition of the mutantallele and selective inhibition of mutant protein expression.

HTT is a large protein, with a molecular weight of ˜348 kDa. Unaffectedindividuals have up to 35 repeats, while HD patients can have from 36to >100 repeats. The molecular weight difference between mutant andwild-type protein is no more than several kDa, complicating resolutionof the proteins by SDS-PAGE. The inventors found that 5% Tris-acetatepolyacrylamide gels allowed clean separation of wild-type and mutant HTTin GM04281 patient-derived fibroblast cells (wild-type allele/17repeats, mutant allele/69 repeats) (FIG. 1B).

The inventors synthesized peptide nucleic acid (PNA)-peptide conjugatestargeting HTT mRNA (Table 1; FIGS. 1C-D). PNAs are a class of DNA/RNAmimic with an uncharged amide backbone that facilitates recognition oftarget sequences within RNA structure (Good and Nielsen, 1998; Marin andArmitage, 2005). PNA conjugates were synthesized to contain a cationicpeptide d-Lys₈ at the C-terminus to promote the import of PNAs intocells (Hu and Corey, 2007). REP, 5J, and 3J-8 were complementary to theCAG repeat or to the 5′ or 3′ junctions between the repeat andsurrounding regions of the HTT gene. The inventors targeted the 3′ and5′ junctions because complementarity to mRNA sequence outside the CAGrepeat may further enhance the specificity for targeting mutant HTTrelative to other cellular proteins. Conjugate +CTL was a positivecontrol targeting the translation start site for HTT, while −CTL1 and−CTL2 were noncomplementary negative controls.

TABLE 1 PNA, siRNA, and LNA oligomers SEQ ID NAME SEQUENCE LENGTH NO:PNA-peptide conjugates: REP K-GCTGCTGCTGCTGCTGCTG-K₈ 19  3 REP-NK₈-GCTGCTGCTGCTGCTGCTG-K 19  4 REP13 K-GCTGCTGCTGCTGCTG-K₈ 16  5 REP16K-GCTGCTGCTGCTG-K₈ 13  6 5J K-GCTGCTGCTGGAAGGACTT-K₈ 19  7 3J-8K-GGCGGCTGTTGCTGCTGCT-K₈ 19  8 3J-10 K-CGGCTGTTGCTGCTGCTGC-K₈ 19  9 3J-6K-GTGGCGGCTGTTGCTGCTG-K₈ 19 10 3J-4 K-CGGTGGCGGCTGTTGCTGC-K₈ 19 11 3J-0K-GCGGCGGTGGCGGCTGTTG-K₈ 19 12 +CTL K-GCTTTTCCAGGGTCGCCAT-K₈ 19 13 −CTL1K-GCTATACCAGCGTCGTCAT-K₈ 19 14 −CTL2 K-ACCTACTGTCCTCGGCACCA-K₈ 20 155J/ATX K-GCTGCTGCTGTTGCTGCTT-K₈ 19 16 3J/ATX K-ATAGGTCCCGCTGCTGCTG-K₈ 1917 siRNAs: siRNA/REP GCUGCUGCUGCUGCUGCUGTT 21 18 siRNA/5JGCUGCUGCUGGAAGGACUUTT 21 19 siRNA/3J GGCGGCUGUUGCUGCUGCUTT 21 20siRNA/+CTL GCUUUUCCAGGGUCGCCAUTT 21 21 siRNA/−CTL1 GCUAUACCAGCGUCGUCAUTT21 22 siRNA/−CTL2 GCAGCUGUUGCUACUGUUGTT 21 23 LNAs: LNA/REPgcTgcTgcTgcTgcTgcTg 19 24 LNA/5J gcTgcTgcTggAagGacTt 19 25 LNA/3JggCggCtgTtgCtgCtgCt 19 26 LNA/+CTL gcTttTccAggGtcGccAt 19 27 LNA/−CTLgcTatAccAgcGtcGtcAt 19 28 PNAs are listed N to C terminal. siRNAs(antisense strands only) and LNAs are listed 5′to 3′. D-amino acids areused in all peptide conjugates. Mismatched bases are underlined. ForLNAs, modified bases are represented as capital letters and DNA basesare lower case.

PNA conjugates REP and 3J-8 inhibited expression of mutant HTT proteinwith IC₅₀ values of 0.3 μM and 1.5 μM respectively (FIG. 2A-C).Selective inhibition of mutant HTT expression by REP persisted for up to14 days (FIG. 2D). This persistent inhibition was achieved even thoughtreated cells went through several rounds of cell division. Addition ofPNA REP did not decrease levels of HTT mRNA (FIGS. 5A-B). It is knowthat the binding of PNAs to mRNA does not reduce RNA levels (Knudsen andNielsen, 1996). By contrast, the binding of PNAs to DNA blockstranscription and reduces RNA levels (Janowski et al., 2005). Thefinding that PNAs do not decrease RNA levels is consistent with amechanism that involves binding to mRNA and blocking translation ratherthan binding to DNA and inhibition of transcription.

Many genes contain CAG repeats, including some that are essential forcellular function. At concentrations sufficient for selective inhibitionof mutant HTT, addition of PNA conjugate REP did not affect expressionof representative CAG repeat-containing genes including TATA box bindingprotein (TBP), AAK1, and POU3F2 (FIG. 2E) and did not cause cellulartoxicity or affect rates of cell proliferation.

To test the consequences of selectively inhibiting expression of mutantHTT protein on phenotypes related to HD, the inventors added REP toprimary neuronal cell (medium spiny striatal neurons, MSN) culturesderived from YAC128 transgenic mice (FIG. 6; FIG. 2F) (Slow et al.,2003; Tang et al., 2005). In this model, full length human HTT mRNAcontaining 128 CAG repeats is expressed under control of its endogenouspromoter in mice that also express wild-type murine huntingtin. MSNcells expressing mutant HTT protein are more susceptible to apoptosisupon addition of glutamate (Tang et al., 2005). Following exposure to250 μM glutamate, the fraction of apoptotic WT MSN was increased to30-40% and the fraction of apoptotic YAC128 MSN was increased to 60-70%.Addition of REP was neuroprotective, reducing the percentage ofapoptotic YAC128 cells to −40%, similar to levels seen in wild-type MSN.Importantly, low levels of apoptotic cell death were observed in theabsence of glutamate, indicating that REP is not toxic to cultured MSNcells at the concentrations used in the inventors' assay.

To examine strategies for optimizing selective inhibition of HTTexpression, the inventors examined additional PNA inhibitors, duplexRNAs, and single-stranded locked nucleic acids (LNAs). They testedPNA-peptide conjugates that were 16 (REP16) and 13 (REP13) bases inlength that target the CAG repeat and observed that both shorter PNAswere potent and selective inhibitors with IC₅₀ values of 0.4 μM and 0.5μM respectively (FIG. 3A-B). The inventors also observed selectiveinhibition when the cationic peptide d-Lys₈ was connected to a PNA atits N- rather than the C-terminus, although switching the orientation ofthe peptide raised the IC₅₀ value to 2.5 μM (FIG. 3C). For PNAs thattarget sequences that systematically extend outward from the CAG repeatthrough the 3′ junction, the efficiency of inhibition decreases as PNAshave less complementarity to the CAG repeat (FIG. 3D). These datasuggest that modification strategy, PNA size, and target location affectpotency of inhibition.

Duplex RNAs are currently being tested in clinical trials and havedemonstrated promising features for drug development (Corey, 2007). Thepotency and widespread use of siRNAs makes them a good benchmark forevaluating the effectiveness of PNAs. To test whether siRNAs would alsoachieve selective inhibition of mutant HTT, the inventors introducedduplex RNAs analogous in sequence to PNAs REP, 5J, and 3J into GM04281fibroblast cells. In contrast to the selective inhibition of HTTexpression observed for PNAs, duplex RNAs showed little selectivity(FIGS. 7A-D).

The inventors also tested oligonucleotides that contain locked nucleicacid (LNA) bases (Vester and Wengel, 2004). LNA is an RNA analog thatcontains a methylene bridge between the 2′ oxygen of the ribose and the4′-carbon (FIG. 1C). This bridge reduces the conformational flexibilityof the ribose and confers outstanding affinity to complementaryhybridization. Unlike PNAs, LNA oligomers are being tested in clinicaltrials (Corey, 2007; Frieden and Orum, 2006) and this experience mayhelp facilitate clinical development of anti-HTT oligomers. Theinventors used cationic lipid to introduce LNAs into cells and observedselective inhibition of mutant HTT by LNA/REP or LNA/3J (FIG. 3D; FIG.8). As had been observed for PNAs, concentrations of LNA that blockselectively expression of mutant HTT did not affect other genes thatcontain CAG repeats (FIG. 3F).

HD is one of many diseases caused by an expansion of triplet repeats.Another example is spinocerebellar ataxia type 3 (Machado-JosephDisease) (Kieling et al., 2007; Paulson, 2007; Bichelmeier et al.,2007). The disease is usually first noted in adults with patientseventually becoming wheelchair-bound or bedridden. It is one of the mostcommon ataxias (Bichelmeier et al., 2007). The disease is caused byexpanded CAG repeats (12-39 repeats are normal, beyond 45 repeatsindicates disease) within the gene encoding ataxin-3. Ataxin-3 is adeubiquinating enzyme and the expanded repeat may promote proteinaggregation directly by enhancing self-association of ataxin-3 andindirectly by disrupting normal proteosome processing of ataxin-3substrates (Burnett and Pittman, 2005; Winborn et al., 2008).Interactions between the mutant RNA and cellular proteins may alsocontribute to the mutant phenotype (Li et al., 2008).

The inventors obtained patient-derived cell line GM06151 that isheterozygous for an expanded CAG repeat (wild-type allele/24 repeats,mutant allele/74 repeats). The inventors tested PNA conjugates thattargeted the CAG repeat region (REP and REP13), the 5′ junction(5J/ATX), and the 3′ junction (3J/ATX) (FIG. 4A). PNA peptide conjugatesREP and REP13 that are complementary to the CAG repeat selectivelyinhibited mutant ataxin-3 with IC₅₀ values of 0.3 μM and 0.5 μMrespectively (FIG. 4B-C). Conjugates that target the 3′ and 5′ junctionswere also selective inhibitors with IC₅₀ values of 1.5 μM and 0.4 μMrespectively (FIGS. 4D-E). These data suggest that the inventors'strategy can be extended beyond HTT to other therapeutic targets. Theinventors also tested siRNA/REP. Similar to observations for inhibitionof HTT protein (FIGS. 7A-D), this RNA was an effective inhibitor ofataxin-3 expression but did not selectively reduce levels of mutantprotein (FIG. 9).

The inventors also directly compared PNA REP19 and LNA/REP19 with thebest RNA identified by Friedlander (RNA S4) and co-workers in theGM09197 cell line used by Friedlander. This cell line has 151 CAGrepeats within the mutant allele, and 21 repeats in the wild-typeallele. They did not test RNA S4 in the other cell lines used for thesestudies because they either do not contain the polymorphism (and wouldtherefore not be susceptible to the action of S4) or have not beencharacterized. Both RNA S4 and LNA/REP19 were introduced into cellsusing cationic lipid, permitting a direct comparison of potency.

The inventors confirmed that RNA S4 as an allele-selective inhibition ofmutant HTT, with an IC₅₀ value of 50 nM and a maximum efficacy of 60%for inhibition of mutant HTT. No inhibition of wild-type HTT wasobserved (data now shown). LNA/REP19 was more potent with an IC₅₀ valueof 4 nM for inhibition of mutant HTT and a maximum efficacy of 100%(data now shown). LNA/REP19 yielded 30% inhibition of wild-type HTTexpression when 100 nM LNA was added. At concentrations of over 100 nM,the combination of lipid and RNA S4 or LNA/REP19 begins to be toxic tocells.

The inventors also tested PNAs REP19 and REP19N in GM09197 cells. Directcomparison of IC₅₀ values of PNA REP19 with LNA/REP19 or siRNA S4 isimpossible because the PNA is delivered into cells using an attachedpeptide rather than cationic lipid. However quantifying inhibitionallows general trends to be observed. REP19 inhibits mutant HTT with anIC₅₀ value of 240 nM and a selectivity of 5.4-fold relative toinhibition of wild-type HTT (data now shown). REP19N inhibits mutant HTTwith an 1C₅₀ value of 1.2 μM and little inhibition of wild-type HTT. Thepotencies and selectivities towards inhibition of mutant HTT in GM09197cells are slightly better than in the other cell lines, consistent withGM09197 cells expressing HTT mRNA with a greater number of CAG repeats.

The inventors synthesized thirteen base PNAs containing one, two, three,or four PhpC (FIG. 10) substitutions (Table 2). Their sequences werecomplementary to the CAG repeat within HTT mRNA. All PNAs weresynthesized to contain eight lysine residues in the D-configuration(D-K₈) to facilitate cellular uptake. Many peptides can facilitateuptake of PNAs. They chose D-K₈ because it was both effective andsynthetically simple to add.

TABLE 2 T_(m) data for PNA/RNA duplexes and IC₅₀ values forinhibition of HTT expression in fibroblast cells # of PhpC T_(m)(ΔTm)IC₅₀/mut IC₅₀/wt PNA Sequence bases ° C. (μM) (μM) I GCTGCTGCTGCTG 082.9 0.47 ± 0.2 >2 (SEQ ID NO: 6) II GXTGCTGCTGCTG 1 84.5 (1.6)  0.54 ±0.05 1.68 ± 0.7 (SEQ ID NO: 31) III GCTGCTGXTGCTG 1 86.4 (3.5)  0.71 ±0.07 1.86 ± 0.1 (SEQ ID NO: 32) IV GXTGCTGXTGCTG 2 83.9 (1.0)  0.58 ±0.05  1.3 ± 0.1 (SEQ ID NO: 33) V GXTGXTGXTGCTG 3 >87 (>4.0) 0.97 ±0.2 >4 (SEQ ID NO: 34) VI GXTGXTGXTGXTG 4 >87 (>4.0)  2.6 ± 0.7 >4(SEQ ID NO: 35) PNAs are listed N to C terminal. All PNAs have oneD-lysine at the N terminus, and eight D-lysines at the C terminus. PhpCbases (X) are underlined. T_(m) measurements used complementary RNAoligomers. Mismatch control PNA GCCACTACTGATA (SEQ ID NO: 36) was usedfor comparison.

Introduction of PhpC bases increased thermal stability (Table 2).Increases ranged for 0.5 to 1° C. per substitution and from 1 to >4° C.overall. The measured T₁ reflects basepairing between the PNA and RNAstrands and the interactions between the D-K₈ cationic peptide and thephosphodiester backbone of RNA.

To examine inhibition of HTT, the inventors introduced the modified PNAsinto GM04281 cells. GM04281 is a patient derived fibroblast cell linewith 17 CAG repeats within the wild-type allele and 69 repeats withinthe mutant allele. As an initial screen, the inventors tested PNAs I-VIat a concentration of 1 PhpC-modified PNAs selectively inhibited HTTexpression, but selectivity and/or potency appeared to decrease with thenumber of PhpC substitutions (FIG. 11A).

To further investigate the activity of the modified PNAs, the inventorsexamined inhibition of HTT expression over a range of concentrations(O-4 μM) (FIGS. 11B-F). PNA-peptide conjugate I with no PhpCsubstitutions was able to selectively inhibit mutant HTT expression withan IC₅₀ value of 0.47 μM and a >4 fold selectivity relative inhibitionof the wild-type allele (Table 2) (Hu et al., 2009a). They observed thatintroduction of one or two PhpC bases (PNAs II, III, and IV) did notgreatly affect the potency of inhibition of mutant HTT, slightlyincreased the potency of inhibition of wild-type HTT, and therefore didnot improve selectivity. Introduction of three or four PhpC bases (PNAsV and VI) significantly decreased the potency of both mutant andwild-type HTT expression. Of the five PhpC-modified PNAs tested,triply-substituted PNA V had the best selectivity profile. Greater than50% inhibition of mutant HTT was achieved at concentrations above 1 μM,while greater than 50% inhibition of wild-type HTT was not observed atany concentration tested.

An advantage of PhpC bases is that they are fluorescent. This propertyallows oligomers that contain PhpC to be tracked inside cells byfluorescent microscopy without the need to attach an additionalfluorophore. Previous studies have used microscopy to track PNAs insidecells and have suggested localization to endosomes (Shiraishi et al.,2005; Kaihatsu et al., 2004; Lebleu et al., 2007; Koppelhus et al.,2008; Wolf et al., 2006; Abes et al., 2006). These studies, however,have used PNAs tagged with fluorescent groups that might alterlocalization. An example of how fluorescent tags can alter localizationis provided by one recent study revealing that fluoroscein can redirecta ruthenium-octaarginine conjugate from endosomal to nuclearlocalization (Puckett and Barton, 2009). Another report noted thatfluorescent dyes can alter intracellular localization ofcell-penetrating peptides (Szeto et al., 2005). By using PhpC, the sameoligomer can be used for both gene silencing and localization,permitting more definitive conclusions.

The inventors added doubly-modified PNA II to GM04281 cells and usedconfocal fluorescent microscopy to visualize uptake. Living cells wereused because chemical fixation of cells can cause fluorescent compoundsto spread and prevent an accurate assessment of localization (Bclitskyet al., 2002). The showed that uptake of PNA II was concentrated incompartments outside the periphery of the nucleus after one day (FIG.12A). A similar pattern of fluorescence could be observed nine daysafter administration of PNA conjugate to cells (FIG. 12B), even thoughcells double 3-4 times during this period, substantially diluting thePNA. These data suggest that PNA-peptide conjugates are long-lived butthat simply allowing them to remain inside cells over long periods oftime and repeated cell divisions is not sufficient to release much ofthe conjugate from confinement within endosomes to the cytosol.

These results have significant implications for interpretation of priorstudies of PNA localization. The finding that PNAs modified with PhpCshow the same intracellular distribution as PNAs modified with terminalfluorescent groups suggests that previous observations of PNAlocalization reflect the localization of the PNAs themselves and werenot substantially influenced by the attached fluorophores.

To estimate the location of cellular uptake, the inventors treated cellswith both PhpC-modified PNA and transferrin, a marker for endosomallocalization. They observed that uptake of PhpC-modified PNA andtransferrin were co-localized, suggesting that both largely reside inthe endosome and enter cells through similar uptake mechanisms (FIGS.12A-C). Images were obtained fifteen hours after treatment withPNA/transferrin, and some of the overlap may arise from lysosomes.Endosomal/lysosomal localization for fluorescently-labeled PNA-peptideconjugates has been reported previously (Shiraishi et al., 2005;Kaihatsu et al., 2004; Lebleu et al., 2007; Koppelhus et al., 2008; Wolfet al., 2006; Abes et al., 2006), and these results suggest that PNAconjugates containing PhpC follow a similar uptake route.

While these data indicate that most PNA is confined within endosomes,our observation of PNA-mediated inhibition demonstrates that some PNAescapes. Increasing the efficiency endosomal escape, either throughaddition of compounds that promote endosomal release (Shiraishi et al.,2005) or through chemical modification to the PNA (Koppelhus et al.,2008; Hu and Corey, 2007), remains a significant goal for research. Theinventors also note that fluorescence is not a quantitative tool forjudging the relative amount of PNA in the cytosol and endosomes becausefluorescent material in the cytosol might be quenched by associationwith nucleic acids. The actual distribution of PNA to the cytosol may behigher than is apparent from the micrographs.

These data show that PhpC bases can increase T_(m) values for antisensePNAs and modify their activities inside cells. The sensitivity of bothT_(m) and IC₅₀ values to the exact number and placement of PhpC basesemphasizes the usefulness of the modification as a tool for tailoringPNA properties.

Addition of PhpC bases to PNAs targeting the CAG repeat within HTT mRNAdid not increase allele-selectivity, and in some cases reduced eitherpotency or selectivity or both. It is not clear why modifications thatincrease binding affinity should decrease the potency of recognition.One possibility is the modified PNAs form stronger self-complementaryinteractions that compete with intermolecular binding to mRNA. Thisexplanation is especially relevant to the sequence used in this studybecause it contains a triplet repeat that tends to form aself-complementary hairpin structure.

The triplet repeat within HTT mRNA is a special target. It is possiblethat other nucleic acid targets, such as nonrepetitive sequenceschromosomal DNA or mRNA, might be more advantageous ones for recognitionby PNAs modified with PhpC bases. Alternatively, the exact placement ofPhpC bases may not be optimal. The inventors have previouslydemonstrated that attaching the D-K8 peptide to the PNA N- rather thanC-termini can dramatically enhance allele-selectivity (Hu et al., 2009a;Hu et al., 2009b), and it is possible that similar simple changes inPhpC placement may also yield improved results.

* * *

All of the compositions and/or methods disclosed and claimed herein canbe made and executed without undue experimentation in light of thepresent disclosure. While the compositions and methods of this inventionhave been described in terms of preferred embodiments, it will beapparent to those of skill in the art that variations may be applied tothe compositions and/or methods and in the steps or in the sequence ofsteps of the method described herein without departing from the concept,spirit and scope of the invention. More specifically, it will beapparent that certain agents which are both chemically andphysiologically related may be substituted for the agents describedherein while the same or similar results would be achieved. All suchsimilar substitutes and modifications apparent to those skilled in theart are deemed to be within the spirit, scope and concept of theinvention as defined by the appended claims.

V. REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

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The invention claimed is:
 1. A nucleic acid analog that targets an mRNAencoding an expanded tri-nucleotide repeat region for a disease proteinand inhibits expression of the disease protein, wherein inhibition (i)is selective for the disease protein, and (ii) does not substantiallyaffect synthesis of the disease protein mRNA.
 2. The nucleic acid analogof claim 1, wherein said nucleic acid analog further targets a repeatregion junction.
 3. The nucleic acid analog of claim 1, wherein saidnucleic acid analog is about 7 to about 30 bases in length.
 4. Thenucleic acid analog of claim 1, wherein said nucleic acid analog is apeptide-nucleic acid (PNA).
 5. The nucleic acid analog of claim 4,wherein said PNA further comprises a cationic peptide.
 6. The nucleicacid analog of claim 1, wherein said nucleic acid analog is a lockednucleic acid (LNA).
 7. The nucleic acid analog of claim 6, wherein saidLNA further comprises a cationic peptide.
 8. The nucleic acid analog ofclaim 1, wherein said nucleic acid analog lacks bases that recruitRNAseH.
 9. The nucleic acid analog of claim 1, wherein said nucleic acidanalog is dispersed in a lipid vehicle.
 10. The nucleic acid analog ofclaim 1, wherein said nucleic acid analog is disposed in apharmaceutically acceptable buffer or diluent.
 11. The nucleic acidanalog of claim 1, wherein the sequence is gcTgcTgcTgcTgcTgcTg (SEQ IDNO: 3), wherein uppercase T indicates a locked nucleic acid.
 12. Thenucleic acid analog of claim 1, wherein the sequence iscTgcTgcTgcTgcTgcTgc (SEQ ID NO: 37), wherein uppercase T indicates alocked nucleic acid.
 13. The nucleic acid analog of claim 1, wherein thesequence is TgcTgcTgcTgcTgcT (SEQ ID NO: 38), wherein uppercase Tindicates a locked nucleic acid.